Fix check_dependencies for Ubuntu 12.10 and ...

... and other platforms that report a different arch triplet than where
they store their libraries)

check-dependencies.sh doesn't find glib2 on Ubuntu 12.10 since glib is
installed in /usr/lib/i386-linux-gnu/glib-2.0/include/glibconfig.h while
gcc -dumpmachine reports the arch as i686-linux-gnu