https://hg.mozilla.org/mozilla-central/rev/e8c173a632a4
https://hg.mozilla.org/mozilla-central/rev/dbeb248015cc
https://hg.mozilla.org/mozilla-central/rev/de7abe2c2b3e

--- a/build/moz.configure/toolchain.configure
+++ b/build/moz.configure/toolchain.configure
@@ -1331,10 +1331,6 @@ def lto(value, c_compiler):
 
     # clang and clang-cl
     if c_compiler.type in ('clang', 'clang-cl'):
-        # Until Bug 1457168 is fixed, we have to hardcode -fuse-ld=lld here
-        if c_compiler.type == 'clang':
-            flags.append("-fuse-ld=lld")
-
         if len(value) and value[0].lower() == 'full':
             flags.append("-flto")
             ldflags.append("-flto")
@@ -1362,8 +1358,6 @@ add_old_configure_assignment('MOZ_LTO', lto.enabled)
 add_old_configure_assignment('MOZ_LTO_CFLAGS', lto.flags)
 add_old_configure_assignment('MOZ_LTO_LDFLAGS', lto.ldflags)
 
-imply_option('--enable-linker', 'lld', when='--enable-lto')
-
 # ASAN
 # ==============================================================
 
@@ -1566,7 +1560,7 @@ set_config('CARGO_INCREMENTAL', cargo_incremental)
 
 @depends(target)
 def is_linker_option_enabled(target):
-    if target.kernel not in ('Darwin', 'WINNT', 'SunOS'):
+    if target.kernel not in ('WINNT', 'SunOS'):
         return True
 
 
@@ -1578,21 +1572,40 @@ option('--enable-gold',
 imply_option('--enable-linker', 'gold', when='--enable-gold')
 
 js_option('--enable-linker', nargs=1,
-          help='Select the linker {bfd, gold, lld, lld-*}',
+          help='Select the linker {bfd, gold, ld64, lld, lld-*}',
           when=is_linker_option_enabled)
 
 
 @depends('--enable-linker', c_compiler, developer_options, '--enable-gold',
-         extra_toolchain_flags, when=is_linker_option_enabled)
+         extra_toolchain_flags, target, lto.enabled,
+         when=is_linker_option_enabled)
 @checking('for linker', lambda x: x.KIND)
 @imports('os')
 @imports('shutil')
 def select_linker(linker, c_compiler, developer_options, enable_gold,
-                  toolchain_flags):
-
-    linker = linker[0] if linker else None
+                  toolchain_flags, target, lto):
+
+    if linker:
+        linker = linker[0]
+    elif lto and c_compiler.type == 'clang' and target.kernel != 'Darwin':
+        # If no linker was explicitly given, and building with clang for non-macOS,
+        # prefer lld. For macOS, we prefer ld64, or whatever the default linker is.
+        linker = 'lld'
+    else:
+        linker = None
 
-    if linker not in ('bfd', 'gold', 'lld', None) and not linker.startswith("lld-"):
+    def is_valid_linker(linker):
+        if target.kernel == 'Darwin':
+            valid_linkers = ('ld64', 'lld')
+        else:
+            valid_linkers = ('bfd', 'gold', 'lld')
+        if linker in valid_linkers:
+            return True
+        if 'lld' in valid_linkers and linker.startswith('lld-'):
+            return True
+        return False
+
+    if linker and not is_valid_linker(linker):
         # Check that we are trying to use a supported linker
         die('Unsupported linker ' + linker)
 
@@ -1602,13 +1615,34 @@ def select_linker(linker, c_compiler, developer_options, enable_gold,
 
     def try_linker(linker):
         # Generate the compiler flag
-        linker_flag = ["-fuse-ld=" + linker] if linker else []
+        if linker == 'ld64':
+            linker_flag = ['-fuse-ld=ld']
+        elif linker:
+            linker_flag = ["-fuse-ld=" + linker]
+        else:
+            linker_flag = []
         cmd = cmd_base + linker_flag + version_check
         if toolchain_flags:
             cmd += toolchain_flags
 
-        cmd_output = check_cmd_output(*cmd).decode('utf-8')
-        if 'GNU ld' in cmd_output:
+        # ld64 doesn't have anything to print out a version. It does print out
+        # "ld64: For information on command line options please use 'man ld'."
+        # but that would require doing two attempts, one with --version, that
+        # would fail, and another with --help.
+        # Instead, abuse its LD_PRINT_OPTIONS feature to detect a message
+        # specific to it on stderr when it fails to process --version.
+        env = dict(os.environ)
+        env['LD_PRINT_OPTIONS'] = '1'
+        retcode, stdout, stderr = get_cmd_output(*cmd, env=env)
+        cmd_output = stdout.decode('utf-8')
+        stderr = stderr.decode('utf-8')
+        if retcode == 1 and 'Logging ld64 options' in stderr:
+            kind = 'ld64'
+
+        elif retcode != 0:
+            return None
+
+        elif 'GNU ld' in cmd_output:
             # We are using the normal linker
             kind = 'bfd'
 
@@ -1627,13 +1661,21 @@ def select_linker(linker, c_compiler, developer_options, enable_gold,
         )
 
     result = try_linker(linker)
+    if result is None:
+        if linker:
+            die("Could not use {} as linker".format(linker))
+        die("Failed to find a linker")
 
     if (linker is None and enable_gold.origin == 'default' and
             developer_options and result.KIND == 'bfd'):
-        gold = try_linker('gold')
-
-        if gold.KIND == 'gold':
-            result = gold
+        # try and use lld if available.
+        tried = try_linker('lld')
+        if tried is None or tried.KIND != 'lld':
+            tried = try_linker('gold')
+            if tried is None or tried.KIND != 'gold':
+                tried = None
+        if tried:
+            result = tried
 
     # If an explicit linker was given, error out if what we found is different.
     if linker and not linker.startswith(result.KIND):
@@ -1644,7 +1686,7 @@ def select_linker(linker, c_compiler, developer_options, enable_gold,
 
 set_config('LD_IS_BFD', depends(select_linker.KIND)
            (lambda x: x == 'bfd' or None))
-set_config('LINKER_LDFLAGS', select_linker.LINKER_FLAG)
+add_old_configure_assignment('LINKER_LDFLAGS', select_linker.LINKER_FLAG)
 
 
 js_option('--enable-clang-plugin', env='ENABLE_CLANG_PLUGIN',
--- a/build/moz.configure/util.configure
+++ b/build/moz.configure/util.configure
@@ -19,20 +19,13 @@ def configure_error(message):
     their inputs from moz.configure usage.'''
     raise ConfigureError(message)
 
-# A wrapper to obtain a process' output that returns the output generated
-# by running the given command if it exits normally, and streams that
-# output to log.debug and calls die or the given error callback if it
-# does not.
-
 
+# A wrapper to obtain a process' output and return code.
+# Returns a tuple (retcode, stdout, stderr).
 @imports(_from='__builtin__', _import='unicode')
 @imports('subprocess')
-@imports('sys')
-@imports(_from='mozbuild.configure.util', _import='LineIO')
 @imports(_from='mozbuild.shellutil', _import='quote')
-def check_cmd_output(*args, **kwargs):
-    onerror = kwargs.pop('onerror', None)
-
+def get_cmd_output(*args, **kwargs):
     # subprocess on older Pythons can't handle unicode keys or values in
     # environment dicts. Normalize automagically so callers don't have to
     # deal with this.
@@ -49,12 +42,24 @@ def check_cmd_output(*args, **kwargs):
 
         kwargs['env'] = normalized_env
 
+    log.debug('Executing: `%s`', quote(*args))
+    proc = subprocess.Popen(args, stdout=subprocess.PIPE,
+                            stderr=subprocess.PIPE, **kwargs)
+    stdout, stderr = proc.communicate()
+    return proc.wait(), stdout, stderr
+
+
+# A wrapper to obtain a process' output that returns the output generated
+# by running the given command if it exits normally, and streams that
+# output to log.debug and calls die or the given error callback if it
+# does not.
+@imports(_from='mozbuild.configure.util', _import='LineIO')
+@imports(_from='mozbuild.shellutil', _import='quote')
+def check_cmd_output(*args, **kwargs):
+    onerror = kwargs.pop('onerror', None)
+
     with log.queue_debug():
-        log.debug('Executing: `%s`', quote(*args))
-        proc = subprocess.Popen(args, stdout=subprocess.PIPE,
-                                stderr=subprocess.PIPE, **kwargs)
-        stdout, stderr = proc.communicate()
-        retcode = proc.wait()
+        retcode, stdout, stderr = get_cmd_output(*args, **kwargs)
         if retcode == 0:
             return stdout
 
--- a/js/src/old-configure.in
+++ b/js/src/old-configure.in
@@ -63,6 +63,8 @@ dnl ========================================================
 USE_PTHREADS=
 _PTHREAD_LDFLAGS=""
 
+LDFLAGS="$LDFLAGS $LINKER_LDFLAGS"
+
 MOZ_DEFAULT_COMPILER
 
 if test -z "$JS_STANDALONE"; then
--- a/old-configure.in
+++ b/old-configure.in
@@ -78,6 +78,8 @@ dnl ========================================================
 MOZ_USE_PTHREADS=
 _PTHREAD_LDFLAGS=""
 
+LDFLAGS="$LDFLAGS $LINKER_LDFLAGS"
+
 MOZ_DEFAULT_COMPILER
 
 if test "$COMPILE_ENVIRONMENT"; then
--- a/python/mozbuild/mozbuild/frontend/context.py
+++ b/python/mozbuild/mozbuild/frontend/context.py
@@ -384,8 +384,6 @@ class LinkFlags(BaseCompileFlags):
 
         self.flag_variables = (
             ('OS', self._os_ldflags(), ('LDFLAGS',)),
-            ('LINKER', context.config.substs.get('LINKER_LDFLAGS'),
-             ('LDFLAGS',)),
             ('DEFFILE', None, ('LDFLAGS',)),
             ('MOZBUILD', None, ('LDFLAGS',)),
             ('FIX_LINK_PATHS', context.config.substs.get('MOZ_FIX_LINK_PATHS'),
--- a/python/mozbuild/mozbuild/test/frontend/test_emitter.py
+++ b/python/mozbuild/mozbuild/test/frontend/test_emitter.py
@@ -242,7 +242,6 @@ class TestEmitterBasic(unittest.TestCase):
     def test_link_flags(self):
         reader = self.reader('link-flags', extra_substs={
             'OS_LDFLAGS': ['-Wl,rpath-link=/usr/lib'],
-            'LINKER_LDFLAGS': ['-fuse-ld=gold'],
             'MOZ_OPTIMIZE': '',
             'MOZ_OPTIMIZE_LDFLAGS': ['-Wl,-dead_strip'],
             'MOZ_DEBUG_LDFLAGS': ['-framework ExceptionHandling'],
@@ -250,7 +249,6 @@ class TestEmitterBasic(unittest.TestCase):
         sources, ldflags, lib, compile_flags = self.read_topsrcdir(reader)
         self.assertIsInstance(ldflags, ComputedFlags)
         self.assertEqual(ldflags.flags['OS'], reader.config.substs['OS_LDFLAGS'])
-        self.assertEqual(ldflags.flags['LINKER'], reader.config.substs['LINKER_LDFLAGS'])
         self.assertEqual(ldflags.flags['MOZBUILD'], ['-Wl,-U_foo', '-framework Foo', '-x'])
         self.assertEqual(ldflags.flags['OPTIMIZE'], [])