dashboard: don't build x/exp and x/mobile on the plan9 builders

Updates golang/go#11811

Change-Id: I776652a3b980772f34d65d8c245a143814aadb6a
Reviewed-on: https://go-review.googlesource.com/c/build/+/209338
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
diff --git a/dashboard/builders_test.go b/dashboard/builders_test.go
index 94cb7f4..dd4e8fe 100644
--- a/dashboard/builders_test.go
+++ b/dashboard/builders_test.go
@@ -512,17 +512,23 @@
 		// But it's off for now as it's always failing.
 		{b("plan9-386", "go"), none},  // temporarily disabled
 		{b("plan9-386", "net"), none}, // temporarily disabled
+		{b("plan9-386", "exp"), none},
+		{b("plan9-386", "mobile"), none},
 		{b("plan9-386@go1.11", "go"), none},
 		{b("plan9-386@go1.12", "go"), none},
 		{b("plan9-386@go1.11", "net"), none},
 		{b("plan9-386@go1.12", "net"), none},
 		{b("plan9-amd64-9front", "go"), onlyPost},
+		{b("plan9-amd64-9front", "exp"), none},
+		{b("plan9-amd64-9front", "mobile"), none},
 		{b("plan9-amd64-9front@go1.11", "go"), none},
 		{b("plan9-amd64-9front@go1.12", "go"), none},
 		{b("plan9-amd64-9front", "net"), onlyPost},
 		{b("plan9-amd64-9front@go1.11", "net"), none},
 		{b("plan9-amd64-9front@go1.12", "net"), none},
 		{b("plan9-arm", "go"), onlyPost},
+		{b("plan9-arm", "exp"), none},
+		{b("plan9-arm", "mobile"), none},
 		{b("plan9-arm@go1.11", "go"), none},
 		{b("plan9-arm@go1.12", "go"), none},
 		{b("plan9-arm", "net"), onlyPost},