POSTIN

/bin/sh

update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-3.3.6 200303
[ -e /usr/bin/gcc ] || update-alternatives --auto gcc

POSTUN

/bin/sh

if [ ! -f /usr/bin/gcc-3.3.6 ]; then
  update-alternatives --remove gcc /usr/bin/gcc-3.3.6
fi