os: embed "sleep 1" within the test binary itself.

This is an alternative to http://golang.org/cl/4150,
and is motivated by a review comment on that CL.

testKillProcess() tries to build and run the Go equivalent
for "sleep 1". This doesn't work for testing cross compilers
since the Go compiler is not available on the targets. This
change embeds the "sleep 1" functionality within the "os.test"
binary itself.

Change-Id: I6bad513deaa6c9e2704e70319098eb4983f1bb23
Reviewed-on: https://go-review.googlesource.com/4190Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/os/os_test.go

@@ -21,7 +21,6 @@ import (
 	"sync"
 	"syscall"
 	"testing"
-	"text/template"
 	"time"
 )
 
@@ -1328,39 +1327,9 @@ func testKillProcess(t *testing.T, processKiller func(p *Process)) {
 		t.Skipf("skipping on %s", runtime.GOOS)
 	}
 
-	dir, err := ioutil.TempDir("", "go-build")
-	if err != nil {
-		t.Fatalf("Failed to create temp directory: %v", err)
-	}
-	defer RemoveAll(dir)
-
-	src := filepath.Join(dir, "main.go")
-	f, err := Create(src)
-	if err != nil {
-		t.Fatalf("Failed to create %v: %v", src, err)
-	}
-	st := template.Must(template.New("source").Parse(`
-package main
-import "time"
-func main() {
-	time.Sleep(time.Second)
-}
-`))
-	err = st.Execute(f, nil)
-	if err != nil {
-		f.Close()
-		t.Fatalf("Failed to execute template: %v", err)
-	}
-	f.Close()
-
-	exe := filepath.Join(dir, "main.exe")
-	output, err := osexec.Command("go", "build", "-o", exe, src).CombinedOutput()
-	if err != nil {
-		t.Fatalf("Failed to build exe %v: %v %v", exe, err, string(output))
-	}
-
-	cmd := osexec.Command(exe)
-	err = cmd.Start()
+	// Re-exec the test binary itself to emulate "sleep 1".
+	cmd := osexec.Command(Args[0], "-test.run", "TestSleep")
+	err := cmd.Start()
 	if err != nil {
 		t.Fatalf("Failed to start test process: %v", err)
 	}
@@ -1374,6 +1343,15 @@ func main() {
 	}
 }
 
+// TestSleep emulates "sleep 1". It is a helper for testKillProcess, so we
+// don't have to rely on an external "sleep" command being available.
+func TestSleep(t *testing.T) {
+	if testing.Short() {
+		t.Skip("Skipping in short mode")
+	}
+	time.Sleep(time.Second)
+}
+
 func TestKillStartProcess(t *testing.T) {
 	testKillProcess(t, func(p *Process) {
 		err := p.Kill()