Check for 'cc' instead of 'gcc' (since clang is starting to become the default)
Preserve existing configuration files during installation.
This is achieved by renaming any existing configuration files as a pre-install step.
As a post-install step and renamed files are then moved back to their original position (overwriting the config files that came with the installer).
Merge pull request #3 from svniemeijer/macosxpkg

Macosxpkg