gdb: Rebuild

[donald]

gdb produces a warning messages on startup:

buczek@sigusr2:~$ gdb
Traceback (most recent call last):
  File "/usr/share/gdb/python/gdb/__init__.py", line 143, in auto_load_packages
    __import__(modname)
  File "/usr/share/gdb/python/gdb/command/frame_filters.py", line 21, in <module>
    import copy
  File "/usr/local/system/python-2.7.16-0/lib/python2.7/copy.py", line 52, in <module>
    import weakref
  File "/usr/local/system/python-2.7.16-0/lib/python2.7/weakref.py", line 14, in <module>
    from _weakref import (
ImportError: cannot import name _remove_dead_weakref

This seems to be related to an incompatibility between the include files
from python 2.7.16 from /usr/local/system/python2 and /usr/lib/libpython2.7.so
from python2_compat which is based on python 2.7.11.

Add -L to use correct library at link time.
Add -Wl,-rpath= to use correct library at run time.