package/python3: adjust _REMOVE_USELESS_FILES fix for new layout

package/python3: adjust _REMOVE_USELESS_FILES fix for new layout

python3 nowadays appends the triplet to the config-<version>m directory:

echo target/usr/lib/python3.7/config-*
target/usr/lib/python3.7/config-3.7m-powerpc-linux-gnu

Likewise, there is no longer a pyconfig.h:

ls target/usr/lib/python3.7/config-3.7m-powerpc-linux-gnu
config.c  config.c.in  install-sh  libpython3.7m.a  Makefile
makesetup  python-config.py  python.o  Setup  Setup.local

So adjust the removal logic to match.  Use a wildcard rather than
$GNU_TARGET_NAME as buildroot and python3's idea of the triplet doesn't
always match (E.G.  for musl/uclibc).

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>