kasan/Makefile: support LLVM style asan parameters

LLVM doesn't understand GCC-style paramters ("--param asan-foo=bar"), thus
we currently we don't use inline/globals/stack instrumentation when
building the kernel with clang.

Add support for LLVM-style parameters ("-mllvm -asan-foo=bar") to enable
all KASAN features.

Link: http://lkml.kernel.org/r/20171204191735.132544-3-paullawrence@google.com


Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Signed-off-by: Paul Lawrence <paullawrence@google.com>
Reviewed-by: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Greg Hackmann <ghackmann@google.com>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Matthias Kaehlcke <mka@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>