cmd/gotelemetry: fix failing TestDocHelp on mobile operating systems

This test is failing due to not being able to exec. Fix this by porting
a simplified version of the standard library's testenv.MustHaveExec.

Change-Id: I5e09cb2af1be77df8ec4d88be3e2a5a6115d04b6
Reviewed-on: https://go-review.googlesource.com/c/telemetry/+/530979
Run-TryBot: Robert Findley <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Reviewed-by: Peter Weinberger <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
Auto-Submit: Robert Findley <[email protected]>

Author: findleyr

cmd/gotelemetry/help_test.go

@@ -14,6 +14,8 @@ import (
 	"os/exec"
 	"strings"
 	"testing"
+
+	"golang.org/x/telemetry/internal/testenv"
 )
 
 var updateDocs = flag.Bool("update", false, "if set, update docs")
@@ -27,6 +29,8 @@ func TestMain(m *testing.M) {
 }
 
 func TestDocHelp(t *testing.T) {
+	testenv.MustHaveExec(t)
+
 	exe, err := os.Executable()
 	if err != nil {
 		t.Fatal(err)

internal/testenv/testenv.go

@@ -67,3 +67,13 @@ func SkipIfUnsupportedPlatform(t testing.TB) {
 		t.Skip("broken for GOARCH 386")
 	}
 }
+
+// MustHaveExec checks that the current system can start new processes
+// using os.StartProcess or (more commonly) exec.Command.
+// If not, MustHaveExec calls t.Skip with an explanation.
+func MustHaveExec(t testing.TB) {
+	switch runtime.GOOS {
+	case "wasip1", "js", "ios":
+		t.Skipf("skipping test: may not be able to exec subprocess on %s/%s", runtime.GOOS, runtime.GOARCH)
+	}
+}