Add BuiltinsRuntimeLibrary

... and rename SanitizerRuntimeLibrary to LibclangRuntimeLibrary since
some of them are not sanitizers.

Bug: 29275768
Test: m
Change-Id: Id638adea42d22b02438fce26120aa155bea14d42
diff --git a/cc/config/arm64_device.go b/cc/config/arm64_device.go
index f412583..6fdd524 100644
--- a/cc/config/arm64_device.go
+++ b/cc/config/arm64_device.go
@@ -238,7 +238,7 @@
 	return t.toolchainClangCflags
 }
 
-func (toolchainArm64) SanitizerRuntimeLibraryArch() string {
+func (toolchainArm64) LibclangRuntimeLibraryArch() string {
 	return "aarch64"
 }