McCoy is a utility from mozilla to sign update.rdfs of
firefox/thunderbird addons, when you host the update.rdf yourself. You can
download it from the
McCoy-Site.
On my current gentoo-system McCoy wasn't running out of the box. It
failed to start printing the error message:
$ ./mccoy Couldn't load XPCOM.
The fix for me was to install the libpng12 library. On my system only the newer libraries libpng14 and libpng15 were installed. For installing libpng12 in a slot you have to run this as root:
$ emerge =media-libs/libpng-1.2.49 -av --oneshot
Note: see my next blogpost for better instructions