Building nodegit for NodeOS with the cross building toolchain

$ npm install -S nodeos-nodegit

That's are the steps to build Nodegit Instead of node-pre-gyp i used node-gyp with prebuilt-install to make use of precompiled binaries.

1. Setting up the Cross building toolchain
2. Getting some Environment Variables (and defining some of them)
3. Downloading Nodegit (without Submodules)
4. Installing only Nodegit's dependencies
5. Downloading libssh2 (because curl cant download them)
6. Running autoreconf -fi (to get rid of the missing script warning)
7. Configuring libssh2 with openssl
8. Building Nodegit
9. Generating the dist/ and lib/ folder
10. Copying over all to the base folder and unpacking itself
11. Creating corresponding prebuilds for prebuild-install