Support .asm files for assembly

Test: mmma -j external/libjpeg-turbo
Change-Id: Id192dae5d74ecbf500fc668931c37f9b91d25ca4
diff --git a/cc/config/toolchain.go b/cc/config/toolchain.go
index 020a0dd..995c8c6 100644
--- a/cc/config/toolchain.go
+++ b/cc/config/toolchain.go
@@ -66,6 +66,8 @@
 	ClangLdflags() string
 	ClangInstructionSetFlags(string) (string, error)
 
+	YasmFlags() string
+
 	Is64Bit() bool
 
 	ShlibSuffix() string
@@ -127,6 +129,10 @@
 	return ""
 }
 
+func (toolchainBase) YasmFlags() string {
+	return ""
+}
+
 func (toolchainBase) SanitizerRuntimeLibraryArch() string {
 	return ""
 }