Comment # 4 on bug 1131076 from Dominique Leuenberger

the file-trigger script triggering the glib-desktop-schema by now actually
does:

filetriggerin scriptlet (using /bin/sh) -- /usr/share/glib-2.0/schemas
# Too many users complain about schemas compiled with wrong permissions
# when in fact the system just honors there umask setting
# Let's reset umask to 022 for glib-compile-schemas, then reset to
# what the user had configured
UMASK=$(umask)
umask 022
/usr/bin/glib-compile-schemas /usr/share/glib-2.0/schemas
umask $UMASK
unset UMASK


So we know that when our script triggers, we have a sensible umask