misc/cgo/testcshared: cd into work directory before running android command

Hopefully this will fix android build.

Maybe fixes #21513

Change-Id: I98f760562646f06b56e385c36927e79458465b92
Reviewed-on: https://go-review.googlesource.com/56790Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

misc/cgo/testcshared/cshared_test.go

@@ -151,7 +151,8 @@ func adbRun(t *testing.T, adbargs ...string) string {
 		t.Fatalf("trying to run adb command when operating system is not android.")
 	}
 	args := []string{"adb", "shell"}
-	args = append(args, adbargs...)
+	shellcmd := fmt.Sprintf("cd %s; %s", androiddir, strings.Join(adbargs, " "))
+	args = append(args, shellcmd)
 	cmd := exec.Command(args[0], args[1:]...)
 	out, err := cmd.CombinedOutput()
 	if err != nil {