kasan: Makefile: shut up warnings if CONFIG_COMPILE_TEST=y

It might be annoying to constantly see this:

scripts/Makefile.kasan:16: Cannot use CONFIG_KASAN: -fsanitize=kernel-address is not supported by compiler

while performing allmodconfig/allyesconfig build tests.
Disable this warning if CONFIG_COMPILE_TEST=y.

Signed-off-by: Andrey Ryabinin <[e-mail]>
Cc: Michal Marek <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

scripts/Makefile.kasan

···
 		--param asan-instrumentation-with-call-threshold=$(call_threshold))
 
 ifeq ($(call cc-option, $(CFLAGS_KASAN_MINIMAL) -Werror),)
+   ifneq ($(CONFIG_COMPILE_TEST),y)
         $(warning Cannot use CONFIG_KASAN: \
             -fsanitize=kernel-address is not supported by compiler)
+   endif
 else
     ifeq ($(CFLAGS_KASAN),)
-        $(warning CONFIG_KASAN: compiler does not support all options.\
-            Trying minimal configuration)
+        ifneq ($(CONFIG_COMPILE_TEST),y)
+            $(warning CONFIG_KASAN: compiler does not support all options.\
+                Trying minimal configuration)
+        endif
         CFLAGS_KASAN := $(CFLAGS_KASAN_MINIMAL)
     endif
 endif