gconf: Avoid error when trying to delete files that don't exist

gconf: Avoid error when trying to delete files that don't exist

Use "rm -f" in do_install_append() so we don't fail if the files we're
trying to delete have already been removed.  This can happen if the
distro policy suppresses both static libs and .la files.

Signed-off-by: Phil Blundell <pb@pbcl.net>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>