Add USE_CLANG_LLD and use_clang_lld.

* USE_CLANG_LLD is unedefined in current builds.
* When USE_CLANG_LLD is defined to 'true' or '1',
  use clang's lld instead of ld or ld.gold.
* When lld is enabled:
  * ld-only flags are not passed to 'lld'.
  * location_packer is disabled.
  * Use new lld's --pack-dyn-relocs=android.
* When lld does not work:
  * In Android.mk files use LOCAL_USE_CLANG_LLD := false.
  * In Android.bp files use use_clang_lld: false.
* Only arm, arm64, x86, and x86_64_devices have LLD flags;
  all other hosts and targets do not call lld yet.

Bug: 73768157
Test: make checkbuild and boot
Change-Id: I06b8a1e868a600997a7e70fe05c299d751d23d5f

cc/config/clang.go

@@ -83,6 +83,15 @@ var ClangUnknownCflags = sorted([]string{
 	"--enable-stdcall-fixup",
 })
 
+// Ldflags that should be filtered out when linking with clang lld
+var ClangUnknownLldflags = sorted([]string{
+	"-fuse-ld=gold",
+	"-Wl,--icf=safe",
+	"-Wl,--fix-cortex-a8",
+	"-Wl,--no-fix-cortex-a8",
+	"-Wl,-m,aarch64_elf64_le_vec",
+})
+
 var ClangLibToolingUnknownCflags = []string{
 	"-flto*",
 	"-fsanitize*",
@@ -182,6 +191,17 @@ func ClangFilterUnknownCflags(cflags []string) []string {
 	return ret
 }
 
+func ClangFilterUnknownLldflags(lldflags []string) []string {
+	ret := make([]string, 0, len(lldflags))
+	for _, f := range lldflags {
+		if !inListSorted(f, ClangUnknownLldflags) {
+			ret = append(ret, f)
+		}
+	}
+
+	return ret
+}
+
 func inListSorted(s string, list []string) bool {
 	for _, l := range list {
 		if s == l {