util/crossgcc: Patch clang to enable linking x86 bare metal targets

This allows clang to link x86 bare metal targets.

TESTED: Qemu i440fx and q35 boot to payload with both 32 and 64bit code
compiled with clang and LTO enabled with updated linker script.

Change-Id: I943215c8714e392e52ea35667f2bf21e517c4255
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/84032
Reviewed-by: Nico Huber <nico.h@gmx.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Felix Singer <service+coreboot-gerrit@felixsinger.de>

util/crossgcc/patches/clang-18.1.8.src_x86_baremetal.patch

@@ -0,0 +1,29 @@
+diff --git a/lib/Driver/ToolChains/BareMetal.cpp b/lib/Driver/ToolChains/BareMetal.cpp
+index 852e0442..eb84a785 100644
+--- a/lib/Driver/ToolChains/BareMetal.cpp
++++ b/lib/Driver/ToolChains/BareMetal.cpp
+@@ -169,6 +169,12 @@ static bool isPPCBareMetal(const llvm::Triple &Triple) {
+          Triple.getEnvironment() == llvm::Triple::EABI;
+ }
+
++/// Is the triple x86_32 or x86_64 -*-none-elf?
++static bool isX86BareMetal(const llvm::Triple &Triple) {
++  return Triple.isX86() && Triple.getOS() == llvm::Triple::UnknownOS &&
++    Triple.getEnvironmentName() == "elf";
++}
++
+ static void findMultilibsFromYAML(const ToolChain &TC, const Driver &D,
+                                   StringRef MultilibPath, const ArgList &Args,
+                                   DetectedMultilibs &Result) {
+@@ -234,9 +240,10 @@ void BareMetal::findMultilibs(const Driver &D, const llvm::Triple &Triple,
+
+ bool BareMetal::handlesTarget(const llvm::Triple &Triple) {
+   return isARMBareMetal(Triple) || isAArch64BareMetal(Triple) ||
+-         isRISCVBareMetal(Triple) || isPPCBareMetal(Triple);
++    isRISCVBareMetal(Triple) || isPPCBareMetal(Triple) || isX86BareMetal(Triple);
+ }
+
++
+ Tool *BareMetal::buildLinker() const {
+   return new tools::baremetal::Linker(*this);
+ }