Add libclang_rt.asan-mips[64]-android.so

Add the clang asan runtime libraries to the mips and mips64 toolchain
definitions.  Fixes missing symbol build errors on asan_test.

Change-Id: I10c46599af2c7758f4726814920b8881644c6f97
diff --git a/cc/mips_device.go b/cc/mips_device.go
index b2b2ccf..0dbbbd7 100644
--- a/cc/mips_device.go
+++ b/cc/mips_device.go
@@ -234,6 +234,10 @@
 	return "${mipsClangLdflags}"
 }
 
+func (toolchainMips) AddressSanitizerRuntimeLibrary() string {
+	return "libclang_rt.asan-mips-android.so"
+}
+
 func mipsToolchainFactory(arch android.Arch) Toolchain {
 	return &toolchainMips{
 		cflags:               "${mipsCflags}",