[CMake] NSIS builder creating invalid exe

[Gonzalo Garramuño]

I updated my CMakeLists.txt to create an NSIS installer under a Nmake 
Makefile.
The packaging works without errors when run with 'nmake package'.

However, the resulting exe file when run, returns:
Bad file number.

The problem happens on both builds for win32 and win64.
The NSIS installer is 3.0a1 and cmake v3.0.1.