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
diff --git a/cc/config/arm64_device.go b/cc/config/arm64_device.go
index 5bb7749..74c936f 100644
--- a/cc/config/arm64_device.go
+++ b/cc/config/arm64_device.go
@@ -35,6 +35,9 @@
 		"-Wl,--icf=safe",
 	}
 
+	arm64Lldflags = append(ClangFilterUnknownLldflags(arm64Ldflags),
+		"-Wl,-z,max-page-size=4096")
+
 	arm64Cppflags = []string{}
 
 	arm64CpuVariantCflags = map[string][]string{
@@ -81,11 +84,13 @@
 
 	pctx.StaticVariable("Arm64Cflags", strings.Join(arm64Cflags, " "))
 	pctx.StaticVariable("Arm64Ldflags", strings.Join(arm64Ldflags, " "))
+	pctx.StaticVariable("Arm64Lldflags", strings.Join(arm64Lldflags, " "))
 	pctx.StaticVariable("Arm64Cppflags", strings.Join(arm64Cppflags, " "))
 	pctx.StaticVariable("Arm64IncludeFlags", bionicHeaders("arm64"))
 
 	pctx.StaticVariable("Arm64ClangCflags", strings.Join(ClangFilterUnknownCflags(arm64Cflags), " "))
 	pctx.StaticVariable("Arm64ClangLdflags", strings.Join(ClangFilterUnknownCflags(arm64Ldflags), " "))
+	pctx.StaticVariable("Arm64ClangLldflags", strings.Join(ClangFilterUnknownCflags(arm64Lldflags), " "))
 	pctx.StaticVariable("Arm64ClangCppflags", strings.Join(ClangFilterUnknownCflags(arm64Cppflags), " "))
 
 	pctx.StaticVariable("Arm64CortexA53Cflags",
@@ -188,6 +193,10 @@
 	return "${config.Arm64Ldflags}"
 }
 
+func (t *toolchainArm64) ClangLldflags() string {
+	return "${config.Arm64Lldflags}"
+}
+
 func (t *toolchainArm64) ToolchainClangCflags() string {
 	return t.toolchainClangCflags
 }