internal/testenv: add a NeedsGoBuild function

This function will skip tests in test environments where
the go command can't be used to build and run binaries.

This will be used by the test in golang.org/cl/236758

Change-Id: Ie61e8890084179b0e999dd377148693395043191
Reviewed-on: https://go-review.googlesource.com/c/tools/+/236920
Run-TryBot: Michael Matloob <matloob@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Heschi Kreinick <heschi@google.com>
Reviewed-by: Rebecca Stambler <rstambler@golang.org>

internal/testenv/testenv.go

@@ -220,6 +220,27 @@ func NeedsGoPackagesEnv(t Testing, env []string) {
 	NeedsGoPackages(t)
 }
 
+// NeedsGoBuild skips t if the current system can't build programs with ``go build''
+// and then run them with os.StartProcess or exec.Command.
+// android, and darwin/arm systems don't have the userspace go build needs to run,
+// and js/wasm doesn't support running subprocesses.
+func NeedsGoBuild(t Testing) {
+	if t, ok := t.(helperer); ok {
+		t.Helper()
+	}
+
+	NeedsTool(t, "go")
+
+	switch runtime.GOOS {
+	case "android", "js":
+		t.Skipf("skipping test: %v can't build and run Go binaries", runtime.GOOS)
+	case "darwin":
+		if strings.HasPrefix(runtime.GOARCH, "arm") {
+			t.Skipf("skipping test: darwin/arm can't build and run Go binaries")
+		}
+	}
+}
+
 // ExitIfSmallMachine emits a helpful diagnostic and calls os.Exit(0) if the
 // current machine is a builder known to have scarce resources.
 //