Preparation of base-pistachio fails on Ubuntu with dash as /bin/sh as it
does not support non-POSIX features like brace expansion. In this case
expanding in the Makefile via $(addprefix ...) fixes this shortcoming.
With the update to L4ka::Pistachio, we no longer need to patch the
contrib sources. Our patch went upstream in the meanwhile.
Apparently, gcc-4.7 is picky about specifying the '-melf_i386' argument
at the command line of the GCC frontend. We need to make sure to use the
'-Wl,' prefix.
The CML2 configuration system calls 'evn python' and expects version
2.x. So we check if python2 is installed when preparing Pistachio and
use the found version instead.
Fixes#264.
