[Cin] Build from git

[Andrea paz]

> can you post output of 'pkg-config --libs OpenEXR'?
>
> also be sure you have OpenEXR headers installed
$ pkg-config --libs OpenEXR
-pthread -lOpenEXR-3_1 -lOpenEXRUtil-3_1 -lOpenEXRCore-3_1 -lIex-3_1
-lIlmThread-3_1 -lImath-3_1

On Arch there is only the "openexr" package, which provides:

usr/include/OpenEXR/ImfHeader.h and usr/bin/exrheader

I don't know if they fit.