Inherit the parent environment when shelling out to Go.

The recipes need to run with a funny GOROOT and we were clearing the
environment.

BUG=26

Change-Id: If233a16e060533ad3fa6f215ce596456c2d7afa5
Reviewed-on: https://boringssl-review.googlesource.com/7988
Reviewed-by: Adam Langley <agl@google.com>

util/run_android_tests.go

@@ -61,6 +61,7 @@ func goTool(args ...string) error {
 	cmd.Stdout = os.Stdout
 	cmd.Stderr = os.Stderr
 
+	cmd.Env = os.Environ()
 	if *aarch64 {
 		cmd.Env = append(cmd.Env, "GOARCH=arm64")
 	} else {