pgsql: Remove -Wl,-undefined,dynamic_lookup in macOS build.

Remove -Wl,-undefined,dynamic_lookup in macOS build.

We don't need this anymore, and it prevents build-time error checking
that's usually good to have, so remove it. Undoes one change of commit
cac765820.

Unfortunately, it's much harder to get a similar effect on other common
platforms, because we don't want the linker to throw errors for symbols
that will be resolved in the core backend. Only macOS and AIX expect the
core backend executable to be available while linking loadable modules,
so only these platforms can usefully throw errors for unresolved symbols
at link time.

Discussion: <2652(dot)1475512158(at)sss(dot)pgh(dot)pa(dot)us>

Branch
------
master

Details
-------
http://git.postgresql.org/pg/commitdiff/bfe2e847811a4d0a46c8cdf16195c0e5929b6f83

Modified Files
--------------
src/Makefile.shlib | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)