Remove GNU make dependency from postinstall

[exsilium]

As of moving to node-pty, the Windows native build of Cloud9v2 has become a low hanging fruit. Altought the npm i dependency installations are carried out successfully, the last step during postinstall fails due to reliance on GNU make. The Makefile targets are actually using simple unix shell commands.

Proposal is to migrate the required installation Makefile steps to build/postinstall.js and use shelljs commands as platform agnostic substitute.

[sr229]

We can try Grunt steps in place instead.

[exsilium]

Definitely grunt or gulp would be an option as a full featured task runners. I'm still conflicted about adding them as a dependency however just to copy some files. We'll see how this works out...