libs: gdbm: enable/install Berkley DBM compat layer

libs: gdbm: enable/install Berkley DBM compat layer

Python supports both GNU dbm and Berkley DBM.
GNU dbm also has a compatibility layer for Berkeley.

The current Berkley DB in OpenWrt is 4.7 and hasn't been updated in ages.
It's also pretty big.

So, an alternative for Python is to use GNU dbm for both (GNU and Berkley).

Also, removing static shared libraries from the build, to encourage the
usage of the shared ones.

Signed-off-by: Alexandru Ardelean <ardeleanalex@gmail.com>