[PATCH] Makefile: use -Wno-main in the full kernel tree

[Randy Dunlap]

When using gcc (SUSE Linux) 7.5.0 (on openSUSE 15.3), I see a
build warning:

../kernel/trace/trace_osnoise.c: In function 'start_kthread':
../kernel/trace/trace_osnoise.c:1461:8: warning: 'main' is usually a function [-Wmain]
  void *main = osnoise_main;
        ^~~~

Quieten that warning by using "-Wno-main". It's OK to use "main" as a
declaration name in the kernel.

Build-tested on most ARCHes.

Signed-off-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
Suggested-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
Suggested-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Daniel Bristot de Oliveira <bristot@xxxxxxxxxx>
Cc: Masahiro Yamada <masahiroy@xxxxxxxxxx>
Cc: Michal Marek <michal.lkml@xxxxxxxxxxx>
Cc: linux-kbuild@xxxxxxxxxxxxxxx
---
 Makefile |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- linux-next-20210812.orig/Makefile
+++ linux-next-20210812/Makefile
@@ -522,7 +522,7 @@ KBUILD_AFLAGS   := -D__ASSEMBLY__ -fno-P
 KBUILD_CFLAGS   := -Wall -Wundef -Werror=strict-prototypes -Wno-trigraphs \
 		   -fno-strict-aliasing -fno-common -fshort-wchar -fno-PIE \
 		   -Werror=implicit-function-declaration -Werror=implicit-int \
-		   -Werror=return-type -Wno-format-security \
+		   -Werror=return-type -Wno-format-security -Wno-main \
 		   -std=gnu89
 KBUILD_CPPFLAGS := -D__KERNEL__
 KBUILD_RUST_TARGET := $(srctree)/arch/$(SRCARCH)/rust/target.json