[pacman-dev] Fix/enforce PATH with makepkg (required for Python packages)

Usually Python packages use `python` in their PKGBUILD, which results in any activated virtualenv to be used, e.g. from `pep257`: ``` package() { cd "${srcdir}/${pkgname}-${pkgver}" python setup.py install --root="${pkgdir}" --optimize=1 install -m 755 -d "${pkgdir}/usr/share/licenses/${pkgname}" install -m 644 -t "${pkgdir}/usr/share/licenses/${pkgname}" LICENSE-MIT } ``` Activating a virtualenv will add the "python" binary in front of $PATH. I've reported this initially for pacaur at https://github.com/rmarquis/pacaur/issues/400, but it's a problem with makepkg after all. I am using this workaround in /etc/xdg/pacaur/config currently: PATH=/usr/bin:$PATH Cheers, Daniel.