Create dockerfile-nogit

dockerfile for compiling a local folder that contains the sourcecode, instead of pulling a fresh copy every time.

To prepare to compile Havoc in Windows/Linux/Mac Docker for example, in the path of the sourcecode:
    docker build -t portapack -f dockerfile-nogit .

And then:
    docker run -v ${PWD}:/havoc portapack

The bin file will be on the build directory now.