gc: fix for Plan 9 build

R=golang-dev
CC=golang-dev, rsc
https://golang.org/cl/4977045

diff --git a/src/cmd/gc/go.h b/src/cmd/gc/go.h
index 2459e538ec4be64afddbc2dfde7a8a1bb227f525..ad2dd48ffe344bf68eb59d7d6c8969e3fa8a5259 100644 (file)
--- a/src/cmd/gc/go.h
+++ b/src/cmd/gc/go.h
@@ -667,6 +667,7 @@ struct      Magic
 };
 
 typedef struct Prog Prog;
+#pragma incomplete Prog
 
 struct Label
 {