[PATCH 1/2] kconfig: detect LD implementation

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

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@xxxxxxxxxx>
Reviewed-by: Michal Orzel <michal.orzel@xxxxxxx>
---
This was discussed with Jan in:

https://lore.kernel.org/xen-devel/fbe0e0f0-85dd-434b-aca5-fa513b720c0b@xxxxxxxx/

While he would be fine to use the option if it was present, he isn't
convinced tools capabilities should be recorded in Kconfig, and hence
doesn't want to introduce the option himself (I hope I got this worded
right).
---
 xen/Kconfig | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/xen/Kconfig b/xen/Kconfig
index ec2bd9fbcf..134e6e68ad 100644
--- a/xen/Kconfig
+++ b/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)
-- 
2.35.1