build: fix for freebsd, openbsd

TBR=r
CC=golang-dev
https://golang.org/cl/5505052
diff --git a/src/make.bash b/src/make.bash
index 3546c5d..c793956 100755
--- a/src/make.bash
+++ b/src/make.bash
@@ -89,7 +89,7 @@
 (
 	cd "$GOROOT"/src/pkg/runtime
 	./autogen.sh
-	make install  # copy runtime.h to pkg directory
+	gomake install  # copy runtime.h to pkg directory
 ) || exit 1
 
 if $USE_GO_TOOL; then