[PATCH v2 3/4] Makefile: lld: tell clang to use lld

[ndesaulniers]

This is needed because clang doesn't select which linker to use based on
$LD but rather -fuse-ld=lld. This is problematic especially for
cc-ldoption, which checks for linker flag support via invoking the
compiler, rather than the linker.

Link: https://github.com/ClangBuiltLinux/linux/issues/342
Suggested-by: Nathan Chancellor <natechancellor@xxxxxxxxx>
Reviewed-by: Nathan Chancellor <natechancellor@xxxxxxxxx>
Tested-by: Nathan Chancellor <natechancellor@xxxxxxxxx>
Signed-off-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
---
Changes V1->V2:
* add reviewed and tested by tags.
* move this addition up 2 statments so that it's properly added to
  KBUILD_*FLAGS as per Nathan.

 Makefile | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/Makefile b/Makefile
index d3b65e96d183..00e8e01d23fc 100644
--- a/Makefile
+++ b/Makefile
@@ -500,6 +500,9 @@ ifneq ($(GCC_TOOLCHAIN),)
 CLANG_FLAGS	+= --gcc-toolchain=$(GCC_TOOLCHAIN)
 endif
 CLANG_FLAGS	+= -no-integrated-as
+ifneq ($(shell $(LD) --version 2>&1 | head -n 1 | grep LLD),)
+CLANG_FLAGS	+= -fuse-ld=lld
+endif
 KBUILD_CFLAGS	+= $(CLANG_FLAGS)
 KBUILD_AFLAGS	+= $(CLANG_FLAGS)
 export CLANG_FLAGS
-- 
2.20.1.791.gb4d0f1c61a-goog