Build issues

[ncannasse]

Issues with build:

• dumpbin is required in PATH, should maybe auto detect in C:\Program Files (x86)\Microsoft Visual Studio XX.0\VC\bin
• tar uses Windows/System32 one by default instead of Cygwin, and deadlock the app... (PATH should prioritize cygwin over everything else)
• perl ipc system simple needs to be installed with cygwin to compile camlp5
• some extra mingw libs are required to be installed and distributed, I didn't update the Build script yet but I have listed the urls in haxe/config.json (see 5526d8c)

[Simn]

• I've changed the dumpbin error to something more accurate, which I think is good enough.
• We solved the tar problem in tar command hangs #11.
• The uv and mbedtls thing is tracked in Support libuv and mbedtls #5.

That leaves only the annoying perl ipc problem.