dashboard: remove the Windows ARM builder

The host-windows-arm-iotcore builder has been missing for an
extended period of time. Attempts to contact the maintainer have
failed. This removes the builder until we can find a replacement
for windows-arm instances.

Fixes golang/go#38493
For golang/go#38607

Change-Id: Ia7d2168f676a86bced754688b4e2d52e61f3125b
Reviewed-on: https://go-review.googlesource.com/c/build/+/229559
Run-TryBot: Carlos Amedee <carlos@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
diff --git a/dashboard/builders_test.go b/dashboard/builders_test.go
index b773066..542ce69 100644
--- a/dashboard/builders_test.go
+++ b/dashboard/builders_test.go
@@ -712,6 +712,8 @@
 	ports := strings.Fields(string(out))
 
 	done := map[string]bool{}
+	done["windows-arm"] = true // TODO(golang.org/issue/38607) disabled until builder is replaced
+
 	var add bytes.Buffer
 	check := func(term string, isArch bool) {
 		if done[term] {
@@ -780,8 +782,9 @@
 	ports := strings.Fields(string(out))
 
 	done := map[string]bool{}
-	done["nacl-386"] = true // removed in Go 1.14
-	done["nacl-arm"] = true // removed in Go 1.14
+	done["nacl-386"] = true    // removed in Go 1.14
+	done["nacl-arm"] = true    // removed in Go 1.14
+	done["windows-arm"] = true // TODO(golang.org/issue/38607) disabled until builder is replaced
 	check := func(goos, goarch string) {
 		if goos == "android" {
 			// TODO(golang.org/issue/25963): support
@@ -820,7 +823,6 @@
 		if _, ok := done[goosArch]; !ok {
 			t.Errorf("Missing trybot or misc-compile trybot: %q", goosArch)
 		}
-
 	}
 
 	for _, port := range ports {