This changeset allows for cross-compilation of Python packages. Packages
built with buildPythonPackage are not allowed to refer to the build
machine. Executables that have shebangs will refer to the host.
Certain programs, like zim, calibre and now also apparently mercurial,
rely on sys.argv[0] providing not just the script name but the full
path.
The Python docs [1] state the following on the matter:
> argv[0] is the script name (it is operating system dependent whether
this is a full pathname or not).
Therefore, scripts should not expect to receive a full path.
Unfortunately some do. While this can be considered a bug, there doesn't
seem any reason not to provide the full path. Therefore we now provide
the full path.
[1]
https://docs.python.org/3.5/library/sys.html?highlight=sys.argv#sys.argv
