CI: fix builds with clang

meta-clang has a langdale branch now, so unset the explicit refspec.

linux-yocto needs to use non-clang objcopy, apply the change locally
until the commit has been merged into meta-clang's langdale branch.

perf needs some patches backported, until that has been done use gcc to
build perf.

Signed-off-by: Ross Burton <ross.burton@arm.com>

ci/clang.yml

@@ -4,7 +4,6 @@ header:
 repos:
   meta-clang:
     url: https://github.com/kraj/meta-clang
-    refspec: master
     patches:
       pixman:
         repo: meta-arm
@@ -13,3 +12,8 @@ repos:
 local_conf_header:
   clang: |
     TOOLCHAIN = "clang"
+    # Backport d89e06ad94a46f6810d0a8787004b71b8ecaf87d to langdale
+    OBJCOPY:pn-linux-yocto:toolchain-clang = "${HOST_PREFIX}objcopy"
+    # Perf needs fixes backported, use GCC for now
+    # https://lore.kernel.org/linux-perf-users/Y5d4k7fDxfRP7hcN@kernel.org/T/#t
+    TOOLCHAIN:pn-perf = "gcc"