1. Support user-provided values of CC, CFLAGS and LDFLAGS
2. Do not force the use of a static version of libsodium

--- a/Makefile
+++ b/Makefile
@@ -54,20 +54,20 @@
 endif
 
 # Compiler options
-CC       = gcc
+CC       := $(CC)
 # compiling flags here
-CFLAGS   = -g -std=c99 -I$(SRCDIR) -I$(LIBDIR)  -Wall -Wextra -fno-common
+CFLAGS   := $(CFLAGS) -g -std=c99 -I$(SRCDIR) -I$(LIBDIR)  -Wall -Wextra -fno-common
 ifndef MAC_OS
 	CFLAGS += $(shell pkg-config --cflags libsecret-1)
 endif
 TEST_CFLAGS = $(CFLAGS) -I.
 
 # Linker options
-LINKER   = gcc
+LINKER   := $(CC)
 ifdef MAC_OS
 LFLAGS   = -lsodium -largp
 else
-LFLAGS   = -l:libsodium.a -lseccomp -fno-common
+LFLAGS   := $(LDFLAGS) -lsodium -lseccomp -fno-common
 endif
 ifdef HAS_CJSON
 	LFLAGS += -lcjson
@@ -81,7 +81,7 @@
 ifdef MAC_OS
 CLIENT_LFLAGS = -L$(APILIB) -largp -loidc-agent.$(LIBVERSION)
 else
-CLIENT_LFLAGS = -L$(APILIB) -l:$(SHARED_LIB_NAME_FULL) -lseccomp
+CLIENT_LFLAGS = $(LDFLAGS) -L$(APILIB) -l:$(SHARED_LIB_NAME_FULL) -lseccomp
 endif
 ifdef HAS_CJSON
 	CLIENT_LFLAGS += -lcjson
@@ -478,7 +478,7 @@
 ifdef MAC_OS
 	@gcc -dynamiclib -fpic -Wl, -o $@ $(PIC_OBJECTS) -lc
 else
-	@gcc -shared -fpic -Wl,-soname,$(SONAME) -o $@ $(PIC_OBJECTS) -lc
+	@$(LINKER) -shared -fpic -Wl,-soname,$(SONAME) $(LDFLAGS) -o $@ $(PIC_OBJECTS) -lc
 endif
 
 .PHONY: shared_lib