remove parallel build with make.
remove parallel build with make.

On my mac, make would pause and resume only after hitting "Enter".
We should take a look at this later.

firebase/firebase-unity-sdk,firebase/firebase-unity-sdk,firebase/firebase-unity-sdk,firebase/firebase-unity-sdk,firebase/firebase-unity-sdk,firebase/firebase-unity-sdk,firebase/firebase-unity-sdk,firebase/firebase-unity-sdk