test/go: use mkdir -p
diff --git a/test/go/Makefile.am b/test/go/Makefile.am
index 59450ce..3ac1d8b 100644
--- a/test/go/Makefile.am
+++ b/test/go/Makefile.am
@@ -28,7 +28,7 @@
 
 # Thrift for GO has problems with complex map keys: THRIFT-2063
 gopath: $(THRIFT) ThriftTest.thrift
-	mkdir src/gen
+	mkdir -p src/gen
 	$(THRIFTCMD) ThriftTest.thrift
 	$(THRIFTCMD) ../StressTest.thrift
 	ln -nfs ../../../lib/go/thrift src/thrift