dashboard: consider disabled TryBot as not providing test coverage

Some TryBot builders are disabled or configured with a custom
try policy that doesn't test the master branch of the main Go
repository. For example, openbsd-386-68 is configured with:

	tryBot: explicitTrySet("sys"),

So it's only a TryBot for the x/sys repo, not the main one.

Modify TestTryBotsCompileAllPorts to not consider such TryBots
when determining whether a port has sufficient pre-submit test
coverage.

This will help in the next change which re-arranges target
selection between misc-compile TryBots.

For golang/go#32632.

Change-Id: If393610d11b04b75133a4f10f89cfdfff9dbaece
Reviewed-on: https://go-review.googlesource.com/c/build/+/313533
Trust: Dmitri Shuralyov <dmitshur@golang.org>
Run-TryBot: Dmitri Shuralyov <dmitshur@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Heschi Kreinick <heschi@google.com>

dashboard/builders_test.go

@@ -853,22 +853,22 @@ func TestTryBotsCompileAllPorts(t *testing.T) {
 			return
 		}
 		for _, conf := range Builders {
-			os := conf.GOOS()
-			arch := conf.GOARCH()
+			if conf.GOOS() == goos && conf.GOARCH() == goarch &&
+				conf.BuildsRepoTryBot("go", "master", "master") {
 
-			if os == goos && arch == goarch && (conf.tryOnly || conf.tryBot != nil) {
+				// There's a real TryBot for this GOOS/GOARCH pair.
 				done[goosArch] = true
 				break
 			}
 
 			if strings.HasPrefix(conf.Name, "misc-compile-") {
 				re, err := regexp.Compile(conf.allScriptArgs[0])
 				if err != nil {
-					t.Errorf("invalid misc-compile filtering pattern for builder %q: %q",
+					t.Fatalf("invalid misc-compile filtering pattern for builder %q: %q",
 						conf.Name, conf.allScriptArgs[0])
 				}
-
-				if re.MatchString(goosArch) || re.MatchString(goos) {
+				if re.MatchString(goosArch) {
+					// There's a misc-compile TryBot for this GOOS/GOARCH pair.
 					done[goosArch] = true
 					break
 				}