kconfig: detect LD implementation

Detect GNU and LLVM ld implementations. This is required for further
patches that will introduce diverging behaviour depending on the
linker implementation in use.

Note that LLVM ld returns "compatible with GNU linkers" as part of the
version string, so be on the safe side and use '^' to only match at
the start of the line in case LLVM ever decides to change the text to
use "compatible with GNU ld" instead.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Michal Orzel <michal.orzel@arm.com>
Acked-by: Julien Grall <jgrall@amazon.com>

xen/Kconfig

@@ -23,6 +23,12 @@ config CLANG_VERSION
 	int
 	default $(shell,$(srctree)/scripts/clang-version.sh $(CC))
 
+config LD_IS_GNU
+	def_bool $(success,$(LD) --version | head -n 1 | grep -q "^GNU ld")
+
+config LD_IS_LLVM
+	def_bool $(success,$(LD) --version | head -n 1 | grep -q "^LLD")
+
 # -fvisibility=hidden reduces -fpic cost, if it's available
 config CC_HAS_VISIBILITY_ATTRIBUTE
 	def_bool $(cc-option,-fvisibility=hidden)