pgsql: Fix pg_config.h make rule

Fix pg_config.h make rule

According to the Autoconf documentation, there should be a make rule

pg_config.h: stamp-h

so that with the right setup around this, a change in pg_config.h.in
will trigger a rebuild of everything that depends on pg_config.h. But
this doesn't always work, sometimes you need to run make twice to get
everything up to date after a change of pg_config.h.in.

The fix is to write the rule as

pg_config.h: stamp-h ;

instead (with an empty command instead of no command). This is what
Automake-generated makefiles effectively do, so it seems safe to be on
this side.

It's not actually clear why this is (apparently) more correct. It's
been posted to
<http://lists.gnu.org/archive/html/help-make/2012-04/msg00058.html>
without response so far.

Branch
------
master

Details
-------
http://git.postgresql.org/pg/commitdiff/d7b2cd9d40e858778ca93b59383d280e510a01e7

Modified Files
--------------
src/Makefile.global.in | 6 +++---
1 files changed, 3 insertions(+), 3 deletions(-)