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

androidmk/cmd/androidmk/android.go

@@ -157,6 +157,7 @@ func init() {
 			"LOCAL_NO_STANDARD_LIBRARIES":    "no_standard_libs",
 			"LOCAL_PACK_MODULE_RELOCATIONS":  "pack_relocations",
 			"LOCAL_TIDY":                     "tidy",
+			"LOCAL_USE_CLANG_LLD":            "use_clang_lld",
 			"LOCAL_PROPRIETARY_MODULE":       "proprietary",
 			"LOCAL_VENDOR_MODULE":            "vendor",
 			"LOCAL_ODM_MODULE":               "device_specific",