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

Clang does not recognize this compiler option.

Change-Id: Ie10ee7c860aa8ae74b6554385e9e369cbbd6f475
Reported-by: Prasad Sodagudi <psodagud@codeaurora.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Git-commit: c64ba044ed57ea72cc1c7b14a8dcfb6ded5a759c
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Signed-off-by: Prasad Sodagudi <psodagud@codeaurora.org>