As fe0a1dc5 has proved, it is not a good concept to add to libpq
dependencies that would enforce the error output to a central logging
facility because it breaks the promise of reporting the error back to
an application in a consistent way, with the application to potentially
exit() suddenly if using pieces from for example jsonapi.c.  prairiedog
has allowed to report an actual design problem with fe0a1dc5, but it will
not be around forever, so removing logging.c from libpgcommon_shlib is a
simple and much better long-term way to prevent any attempt to load the
central logging in libraries with general purposes.

Author: Michael Paquier
Reviewed-by: Tom Lane
Discussion: https://postgr.es/m/20200928073330.GC2316@paquier.xyz