sys-boot/shim: Fix parallel build

The bundled gnu-efi build is implemented in a buggy way that can break when
built in parallel. We've hit this in the nightly sdk build. Add a patch for it.

The patch has been posted upstream at https://github.com/rhboot/shim/pull/643.

Signed-off-by: Jeremi Piotrowski <jpiotrowski@microsoft.com>

sdk_container/src/third_party/coreos-overlay/sys-boot/shim/files/0001-Fix-parallel-build-of-gnu-efi.patch

@@ -0,0 +1,43 @@
+From f10087671538e8e052f035f011fc826f36f2af3b Mon Sep 17 00:00:00 2001
+From: Jeremi Piotrowski <jpiotrowski@microsoft.com>
+Date: Thu, 29 Feb 2024 10:00:22 +0100
+Subject: [PATCH] Fix parallel build of gnu-efi
+
+When building with make 4.4.1, gnu-efi may be built twice and in parallel:
+
+  $ make -n -j ARCH=x86_64 2>&1 | tee build.log
+  $ grep -e 'make -C gnu-efi' build.log
+  make -C gnu-efi \
+  make -C gnu-efi \
+
+This has been seen to cause linking failures when building libgnuefi.a because
+some object files may end up truncated.
+
+The reason for this is that make interprets multiple targets in the same rule
+as independent and can run the rule multiple times. The solution is to define a
+grouped target with &:, which causes make to behave the way one expects: runs
+the rule once and expects it to create all targets.
+
+Grouped target support was added in make 4.3 released 4 years ago.
+
+Signed-off-by: Jeremi Piotrowski <jpiotrowski@microsoft.com>
+---
+ Makefile | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/Makefile b/Makefile
+index 8283d56..bbf707b 100644
+--- a/Makefile
++++ b/Makefile
+@@ -154,7 +154,7 @@ $(MMSONAME): $(MOK_OBJS) $(LIBS)
+ 	$(LD) -o $@ $(LDFLAGS) $^ $(EFI_LIBS) lib/lib.a
+ 
+ gnu-efi/$(ARCH_GNUEFI)/gnuefi/libgnuefi.a gnu-efi/$(ARCH_GNUEFI)/lib/libefi.a: CFLAGS+=-DGNU_EFI_USE_EXTERNAL_STDARG
+-gnu-efi/$(ARCH_GNUEFI)/gnuefi/libgnuefi.a gnu-efi/$(ARCH_GNUEFI)/lib/libefi.a:
++gnu-efi/$(ARCH_GNUEFI)/gnuefi/libgnuefi.a gnu-efi/$(ARCH_GNUEFI)/lib/libefi.a &:
+ 	mkdir -p gnu-efi/lib gnu-efi/gnuefi
+ 	$(MAKE) -C gnu-efi \
+ 		COMPILER="$(COMPILER)" \
+-- 
+2.39.2
+

sdk_container/src/third_party/coreos-overlay/sys-boot/shim/shim-15.8-r1.ebuild

@@ -22,6 +22,11 @@ DEPEND="
   dev-libs/openssl
   coreos-base/coreos-sb-keys
 "
+
+PATCHES=(
+	"${FILESDIR}/0001-Fix-parallel-build-of-gnu-efi.patch"
+)
+
 src_compile() {
   local emake_args=(
     CROSS_COMPILE="${CHOST}-"