Add ubsan_standalone library name to the toolchain.

and export the library name to make. Refactor the code a bit to avoid repeating the library name
multiple times.

Bug: 22033465
Test: Ran external/clang/build.py for aosp-llvm

Change-Id: I25eb3858eb92e1dd493b09524d559802551b2547
diff --git a/cc/config/toolchain.go b/cc/config/toolchain.go
index c286a9a..5a4e032 100644
--- a/cc/config/toolchain.go
+++ b/cc/config/toolchain.go
@@ -71,7 +71,7 @@
 	ShlibSuffix() string
 	ExecutableSuffix() string
 
-	AddressSanitizerRuntimeLibrary() string
+	SanitizerRuntimeLibraryArch() string
 
 	AvailableLibraries() []string
 }
@@ -125,7 +125,7 @@
 	return ""
 }
 
-func (toolchainBase) AddressSanitizerRuntimeLibrary() string {
+func (toolchainBase) SanitizerRuntimeLibraryArch() string {
 	return ""
 }
 
@@ -188,3 +188,19 @@
 func inList(s string, list []string) bool {
 	return indexList(s, list) != -1
 }
+
+func AddressSanitizerRuntimeLibrary(t Toolchain) string {
+	arch := t.SanitizerRuntimeLibraryArch()
+	if arch == "" {
+		return ""
+	}
+	return "libclang_rt.asan-" + arch + "-android.so"
+}
+
+func UndefinedBehaviorSanitizerRuntimeLibrary(t Toolchain) string {
+	arch := t.SanitizerRuntimeLibraryArch()
+	if arch == "" {
+		return ""
+	}
+	return "libclang_rt.ubsan_standalone-" + arch + "-android.so"
+}