kbuild: gcov: enable -fno-tree-loop-im if supported

Clang does not recognize this compiler option.
Reported-by: Prasad Sodagudi <psodagud@codeaurora.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

Makefile

@@ -623,7 +623,9 @@ all: vmlinux
 
 KBUILD_CFLAGS	+= $(call cc-option,-fno-PIE)
 KBUILD_AFLAGS	+= $(call cc-option,-fno-PIE)
-CFLAGS_GCOV	:= -fprofile-arcs -ftest-coverage -fno-tree-loop-im $(call cc-disable-warning,maybe-uninitialized,)
+CFLAGS_GCOV	:= -fprofile-arcs -ftest-coverage \
+	$(call cc-option,-fno-tree-loop-im) \
+	$(call cc-disable-warning,maybe-uninitialized,)
 export CFLAGS_GCOV CFLAGS_KCOV
 
 # The arch Makefile can set ARCH_{CPP,A,C}FLAGS to override the default