runtime: use go generate for zcallback_windows.go

replacement for CL 180640043

Change-Id: I8ff36645cfcbbda338faf7b29cbfdb95c47d5ec4
Reviewed-on: https://go-review.googlesource.com/1765Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/runtime/runtime2_windows.go

-// Copyright 2009 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 runtime
-
-// TODO(brainman): move generation of zsys_windows_*.s out from cmd/dist/buildruntime.c and into here
-const cb_max = 2000 // maximum number of windows callbacks allowed (must be in sync with MAXWINCB from cmd/dist/buildruntime.c)

src/runtime/wincallback.go

@@ -17,7 +17,7 @@ import (
 
 const maxCallback = 2000
 
-func main() {
+func genasm() {
 	var buf bytes.Buffer
 
 	buf.WriteString(`// generated by wincallback.go; run go generate
@@ -41,3 +41,24 @@ TEXT runtime·callbackasm(SB),7,$0
 		os.Exit(2)
 	}
 }
+
+func gengo() {
+	var buf bytes.Buffer
+
+	buf.WriteString(fmt.Sprintf(`// generated by wincallback.go; run go generate
+
+package runtime
+
+const cb_max = %d // maximum number of windows callbacks allowed
+`, maxCallback))
+	err := ioutil.WriteFile("zcallback_windows.go", buf.Bytes(), 0666)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "wincallback: %s\n", err)
+		os.Exit(2)
+	}
+}
+
+func main() {
+	genasm()
+	gengo()
+}

src/runtime/zcallback_windows.go

+// generated by wincallback.go; run go generate
+
+package runtime
+
+const cb_max = 2000 // maximum number of windows callbacks allowed