https://bugs.gentoo.org/941724
which-hunt
diff '--color=auto' -ru sharutils-4.15.2.old/libopts/m4/libopts.m4 sharutils-4.15.2/libopts/m4/libopts.m4
--- sharutils-4.15.2.old/libopts/m4/libopts.m4	2025-01-22 13:17:52.302369061 +0000
+++ sharutils-4.15.2/libopts/m4/libopts.m4	2025-01-22 13:19:46.096362975 +0000
@@ -114,9 +114,9 @@
   AC_PROG_SED
   [while :
   do
-      POSIX_SHELL=`which bash`
+      POSIX_SHELL=`command -v bash`
       test -x "$POSIX_SHELL" && break
-      POSIX_SHELL=`which dash`
+      POSIX_SHELL=`command -v dash`
       test -x "$POSIX_SHELL" && break
       POSIX_SHELL=/usr/xpg4/bin/sh
       test -x "$POSIX_SHELL" && break
diff '--color=auto' -ru sharutils-4.15.2.old/m4/libopts.m4 sharutils-4.15.2/m4/libopts.m4
--- sharutils-4.15.2.old/m4/libopts.m4	2025-01-22 13:17:52.365018511 +0000
+++ sharutils-4.15.2/m4/libopts.m4	2025-01-22 13:19:17.856525747 +0000
@@ -114,9 +114,9 @@
   AC_PROG_SED
   [while :
   do
-      POSIX_SHELL=`which bash`
+      POSIX_SHELL=`command -v bash`
       test -x "$POSIX_SHELL" && break
-      POSIX_SHELL=`which dash`
+      POSIX_SHELL=`command -v dash`
       test -x "$POSIX_SHELL" && break
       POSIX_SHELL=/usr/xpg4/bin/sh
       test -x "$POSIX_SHELL" && break