rust: Replace -fmin-function-alignment with -falign-functions for bindgen

Commit 5270316 ("kbuild: Use -fmin-function-alignment when
available") introduces `-fmin-function-alignment` if supported to remove
a workaround for gcc not respecting `-falign-functions` for cold
functions. bindgen does not recognize `-fmin-function-alignment` but
`-falign-functions` is sufficient as long as bindgen is LLVM backed. See
c27cd08 ("Compiler attributes: GCC cold function alignment
workarounds").
So replace `-fmin-function-alignment` with `-falign-functions` for
bindgen's C flags.

Fixes: 5270316 ("kbuild: Use -fmin-function-alignment when available")
Signed-off-by: Janne Grunau <j@jannau.net>

Author: jannau

rust/Makefile

@@ -264,7 +264,13 @@ else
 bindgen_c_flags_lto = $(bindgen_c_flags)
 endif
 
-bindgen_c_flags_final = $(bindgen_c_flags_lto) -D__BINDGEN__
+# replace '-fmin-function-alignment' with '-falign-functions'. LLVM does not
+# ignore the latter in cold functions. See:
+# 5270316c9fec ("kbuild: Use -fmin-function-alignment when available")
+# c27cd083cfb9 ("Compiler attributes: GCC cold function alignment workarounds")
+bindgen_c_flags_align = $(subst -fmin-function-alignment=,-falign-functions=,$(bindgen_c_flags_lto))
+
+bindgen_c_flags_final = $(bindgen_c_flags_align) -D__BINDGEN__
 
 quiet_cmd_bindgen = BINDGEN $@
       cmd_bindgen = \