builder: run make single-threaded on windows

Will still honor MAKEFLAGS environment variable if set.

R=golang-dev
CC=bradfitz, golang-dev
https://golang.org/cl/4644049

diff --git a/misc/dashboard/builder/main.go b/misc/dashboard/builder/main.go
index 9377fbe3261105f317aac35d1d0f1d17b0b59122..9a714fe79fae0dbc0fc5ef6e0fed7d3d05720057 100644 (file)
--- a/misc/dashboard/builder/main.go
+++ b/misc/dashboard/builder/main.go
@@ -357,7 +357,10 @@ func (b *Builder) envv() []string {
                "GOROOT_FINAL=/usr/local/go",
        }
        for _, k := range extraEnv {
-               e = append(e, k+"="+os.Getenv(k))
+               s, err := os.Getenverror(k)
+               if err == nil {
+                       e = append(e, k+"="+s)
+               }
        }
        return e
 }
@@ -368,9 +371,14 @@ func (b *Builder) envvWindows() []string {
                "GOOS":         b.goos,
                "GOARCH":       b.goarch,
                "GOROOT_FINAL": "/c/go",
+               // TODO(brainman): remove once we find make that does not hang.
+               "MAKEFLAGS": "-j1",
        }
        for _, name := range extraEnv {
-               start[name] = os.Getenv(name)
+               s, err := os.Getenverror(name)
+               if err == nil {
+                       start[name] = s
+               }
        }
        skip := map[string]bool{
                "GOBIN":   true,