kbuild: add CONFIG_LD_IS_LLD

Similarly to the CC_IS_CLANG config, add LD_IS_LLD to avoid GNU ld
specific logic such as ld-version or ld-ifversion and gain the
ability to select potential features that depend on the linker at
configuration time such as LTO.
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Acked-by: Masahiro Yamada <masahiroy@kernel.org>
[nc: Reword commit message]
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Reviewed-by: Sedat Dilek <sedat.dilek@gmail.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

init/Kconfig

@@ -23,6 +23,9 @@ config LD_VERSION
 config CC_IS_CLANG
 	def_bool $(success,$(CC) --version | head -n 1 | grep -q clang)
 
+config LD_IS_LLD
+	def_bool $(success,$(LD) -v | head -n 1 | grep -q LLD)
+
 config CLANG_VERSION
 	int
 	default $(shell,$(srctree)/scripts/clang-version.sh $(CC))