error: unsupported argument '-mimplicit-it=always' to option 'Wa,'

[agners]

Trying to use AS=clang and CONFIG_THUMB2_KERNEL=y leads to the following errors:

clang-10: error: unsupported argument '-mimplicit-it=always' to option 'Wa,'
make[1]: *** [scripts/Makefile.build:266: scripts/mod/empty.o] Error 1
make[1]: *** Waiting for unfinished jobs....
make: *** [Makefile:1112: prepare0] Error 2

This is due to the kernel build system tries to pass -mimplicit-it=always by using -Wa.

[agners]

That can be fixed by using -mimplicit-it=always for Clang instead. This of course needs to be done compiler specific. I will come up with a patch for this.

--- a/arch/arm/Makefile
+++ b/arch/arm/Makefile
@@ -123,7 +123,8 @@ endif
 AFLAGS_NOWARN  :=$(call as-option,-Wa$(comma)-mno-warn-deprecated,-Wa$(comma)-W)
 
 ifeq ($(CONFIG_THUMB2_KERNEL),y)
-CFLAGS_ISA     :=-mthumb -Wa,-mimplicit-it=always $(AFLAGS_NOWARN)
+CFLAGS_ISA     :=-mthumb -mimplicit-it=always
 AFLAGS_ISA     :=$(CFLAGS_ISA) -Wa$(comma)-mthumb
 # Work around buggy relocation from gas if requested:
 ifeq ($(CONFIG_THUMB2_AVOID_R_ARM_THM_JUMP11),y)

[nickdesaulniers]

duping to #1270