Export TSAN_RUNTIME_LIBRARY make variable

TSAN_RUNTIME_LIBRARY is used by external/clang/Android.mk to get the
name of the per-arch TSAN runtime.  This CL also factors-out common code
out of functions that construct names of the sanitizer libraries.

Test: python external/clang/build.py with all CLs in this topic

Change-Id: Ie5fac242c0d5a9296ab8936db927a4c934061aa4
diff --git a/cc/config/toolchain.go b/cc/config/toolchain.go
index 8fc4a21..5270437 100644
--- a/cc/config/toolchain.go
+++ b/cc/config/toolchain.go
@@ -207,20 +207,24 @@
 	return indexList(s, list) != -1
 }
 
-func AddressSanitizerRuntimeLibrary(t Toolchain) string {
+func SanitizerRuntimeLibrary(t Toolchain, sanitizer string) string {
 	arch := t.SanitizerRuntimeLibraryArch()
 	if arch == "" {
 		return ""
 	}
-	return "libclang_rt.asan-" + arch + "-android.so"
+	return "libclang_rt." + sanitizer + "-" + arch + "-android.so"
+}
+
+func AddressSanitizerRuntimeLibrary(t Toolchain) string {
+	return SanitizerRuntimeLibrary(t, "asan")
 }
 
 func UndefinedBehaviorSanitizerRuntimeLibrary(t Toolchain) string {
-	arch := t.SanitizerRuntimeLibraryArch()
-	if arch == "" {
-		return ""
-	}
-	return "libclang_rt.ubsan_standalone-" + arch + "-android.so"
+	return SanitizerRuntimeLibrary(t, "ubsan_standalone")
+}
+
+func ThreadSanitizerRuntimeLibrary(t Toolchain) string {
+	return SanitizerRuntimeLibrary(t, "tsan")
 }
 
 func ToolPath(t Toolchain) string {
diff --git a/cc/makevars.go b/cc/makevars.go
index 200faff..dcde828 100644
--- a/cc/makevars.go
+++ b/cc/makevars.go
@@ -209,6 +209,7 @@
 		if target.Os.Class == android.Device {
 			ctx.Strict(secondPrefix+"ADDRESS_SANITIZER_RUNTIME_LIBRARY", strings.TrimSuffix(config.AddressSanitizerRuntimeLibrary(toolchain), ".so"))
 			ctx.Strict(secondPrefix+"UBSAN_RUNTIME_LIBRARY", strings.TrimSuffix(config.UndefinedBehaviorSanitizerRuntimeLibrary(toolchain), ".so"))
+			ctx.Strict(secondPrefix+"TSAN_RUNTIME_LIBRARY", strings.TrimSuffix(config.ThreadSanitizerRuntimeLibrary(toolchain), ".so"))
 		}
 
 		// This is used by external/gentoo/...