The generic 'buildPythonPackage' function used to use the build/install command
"easy_install" unconditionally. That didn't work for python-numpy, for
instance, because the package wants "setup.py" run with additional parameters
to determine the fortran compiler of choice. The newly introduced function
argument 'installCommand' allows to implement this. By passing that parameter,
the default build command can be overridden.
svn path=/nixpkgs/trunk/; revision=22786
93b18ceb30