gdb: drop local stripping in favor of top level

Since the top level takes care of stripping for us, and some file formats
cannot be stripped safely (like FLAT which will error out), simply punt
the manual stripping from the gdb package.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Acked-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>