Require env variables during make
Require env variables during make

Check for and require environment varibales used by
the rest of the make script. This should start to help
resolt issue #11.

strazzere/android-unpacker,isee15/android-unpacker,chubbymaggie/android-unpacker,Fors3cDream/android_unpacker,strazzere/android-unpacker,keulraesik/android-unpacker,WooyunDota/android-unpacker,WooyunDota/android-unpacker,tempbottle/android-unpacker,chubbymaggie/android-unpacker,isee15/android-unpacker,Fors3cDream/android_unpacker,keulraesik/android-unpacker,tempbottle/android-unpacker