test: disable a couple of precise GC tests for gccgo

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/41610043

test/deferfin.go

@@ -23,6 +23,10 @@ func main() {
 	if runtime.GOARCH != "amd64" {
 		return
 	}
+	// Likewise for gccgo.
+	if runtime.Compiler == "gccgo" {
+		return
+	}
 	N := 10
 	count := int32(N)
 	var wg sync.WaitGroup

test/fixedbugs/issue5493.go

@@ -31,9 +31,10 @@ func run() error {
 }
 
 func main() {
-	// Does not work on 32-bits due to partially conservative GC.
+	// Does not work on 32-bits, or with gccgo, due to partially
+	// conservative GC.
 	// Try to enable when we have fully precise GC.
-	if runtime.GOARCH != "amd64" {
+	if runtime.GOARCH != "amd64" || runtime.Compiler == "gccgo" {
 		return
 	}
 	count = N