misc/cgo/test: only run setgid test on GNU/Linux

Fixes #3874.

R=golang-dev, nj, r, minux.ma
CC=golang-dev
https://golang.org/cl/6446060

misc/cgo/test/basic.go

@@ -11,7 +11,6 @@ package cgotest
 #include <stdlib.h>
 #include <sys/stat.h>
 #include <errno.h>
-#include <unistd.h>
 
 #define SHIFT(x, y)  ((x)<<(y))
 #define KILO SHIFT(1, 10)
@@ -58,7 +57,6 @@ import "C"
 import (
 	"syscall"
 	"testing"
-	"time"
 	"unsafe"
 )
 
@@ -126,20 +124,6 @@ func testMultipleAssign(t *testing.T) {
 	C.free(unsafe.Pointer(p))
 }
 
-func testSetgid(t *testing.T) {
-	// Issue 3871.
-	c := make(chan bool)
-	go func() {
-		C.setgid(0)
-		c <- true
-	}()
-	select {
-	case <-c:
-	case <-time.After(5 * time.Second):
-		t.Error("setgid hung")
-	}
-}
-
 var (
 	cuint  = (C.uint)(0)
 	culong C.ulong

misc/cgo/test/cgo_linux_test.go

+// Copyright 2012 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package cgotest
+
+import "testing"
+
+func TestSetgid(t *testing.T) { testSetgid(t) }

misc/cgo/test/cgo_test.go

@@ -27,6 +27,5 @@ func Test1328(t *testing.T)                { test1328(t) }
 func TestParallelSleep(t *testing.T)       { testParallelSleep(t) }
 func TestSetEnv(t *testing.T)              { testSetEnv(t) }
 func TestHelpers(t *testing.T)             { testHelpers(t) }
-func TestSetgid(t *testing.T)              { testSetgid(t) }
 
 func BenchmarkCgoCall(b *testing.B) { benchCgoCall(b) }

misc/cgo/test/setgid_linux.go

+// Copyright 2012 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Test that setgid does not hang on GNU/Linux.
+// See http://code.google.com/p/go/issues/detail?id=3871 for details.
+
+package cgotest
+
+/*
+#include <sys/types.h>
+#include <unistd.h>
+*/
+import "C"
+
+import (
+	"testing"
+	"time"
+)
+
+func testSetgid(t *testing.T) {
+	c := make(chan bool)
+	go func() {
+		C.setgid(0)
+		c <- true
+	}()
+	select {
+	case <-c:
+	case <-time.After(5 * time.Second):
+		t.Error("setgid hung")
+	}
+}