cmd/coordinator: add missing BuildRepo check

BuildBranch reporting true does not imply BuildRepo returning true.

Change-Id: I6104aa3e606a95747181b2bf71a191fab080a3fd
Reviewed-on: https://go-review.googlesource.com/c/build/+/165760
Run-TryBot: Elias Naur <mail@eliasnaur.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
diff --git a/cmd/coordinator/coordinator.go b/cmd/coordinator/coordinator.go
index 319d220..99ba2dd 100644
--- a/cmd/coordinator/coordinator.go
+++ b/cmd/coordinator/coordinator.go
@@ -936,6 +936,9 @@
 		if builderInfo.TryOnly || knownToDashboard[b] {
 			continue
 		}
+		if !builderInfo.BuildRepo("go") {
+			continue
+		}
 		if !builderInfo.BuildBranch("go", "master", "") {
 			continue
 		}