cmd/coordinator: test x/mobile on android emu builders; and exp on some

Updates golang/go#23824

Change-Id: Iee70bcbfef6a271fdd26694d848a703a200dc0c0
Reviewed-on: https://go-review.googlesource.com/c/164478
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>

cmd/coordinator/coordinator.go

@@ -1401,9 +1401,17 @@ func skipBuild(br buildgo.BuilderRev) bool {
 		// conditionally.
 		bc, ok := dashboard.Builders[br.Name]
 		return !ok || bc.IsReverse()
-	case "exp", // always broken, depends on mobile which is broken
-		"mobile", // always broken (gl, etc). doesn't compile.
-		"term":   // no code yet in repo,
+	case "mobile":
+		if strings.HasPrefix(br.Name, "android-") {
+			return false
+		}
+		return true
+	case "exp":
+		if strings.HasPrefix(br.Name, "android-") || br.Name == "linux-amd64" {
+			return false
+		}
+		return true
+	case "term": // no code yet in repo
 		return true
 	case "perf":
 		if br.Name == "linux-amd64-nocgo" {
@@ -2482,6 +2490,7 @@ func (st *buildStatus) runSubrepoTests() (remoteErr, err error) {
 	}
 
 	return st.bc.Exec(path.Join("go", "bin", "go"), buildlet.ExecOpts{
+		Debug:  true, // make buildlet print extra debug in output for failures
 		Output: st,
 		Dir:    dir,
 		ExtraEnv: append(st.conf.Env(),

dashboard/builders.go

@@ -1758,7 +1758,10 @@ func init() {
 		Name:     "android-amd64-emu",
 		HostType: "host-android-amd64-emu",
 		Notes:    "Android emulator on GCE",
-		tryBot:   nil, // not yet; TODO: collect timing, deciding test sharding size
+		tryBot: func(proj string) bool {
+			// Only for mobile repo for now, not "go":
+			return proj == "mobile"
+		},
 		env: []string{
 			"GOARCH=amd64",
 			"GOOS=android",