internal/testenv: assume that mobile platforms are small machines

Experiments in CL 488655 suggest that the android builders are capable
of running tests that require 'go build' but do not have enough disk
resources to run gopls regression tests. It seems reasonable to always
assume that mobile platforms are (by definition) resource-constrained.

Change-Id: If91627b681050bb2e53d03a86ce609565ae3dc6f
Reviewed-on: https://go-review.googlesource.com/c/tools/+/488815
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: Bryan Mills <bcmills@google.com>
Reviewed-by: Robert Findley <rfindley@google.com>
Run-TryBot: Bryan Mills <bcmills@google.com>

internal/testenv/testenv.go

@@ -278,7 +278,12 @@ func ExitIfSmallMachine() {
 		// For now, we'll skip them instead.
 		fmt.Fprintf(os.Stderr, "skipping test: %s builder is too slow (https://golang.org/issue/49321)\n", b)
 	default:
-		return
+		switch runtime.GOOS {
+		case "android", "ios":
+			fmt.Fprintf(os.Stderr, "skipping test: assuming that %s is resource-constrained\n", runtime.GOOS)
+		default:
+			return
+		}
 	}
 	os.Exit(0)
 }