pgsql: Fix non-GNU makefiles for AIX make.

Fix non-GNU makefiles for AIX make.

Invoking the Makefile without an explicit target was building every
possible target instead of just the "all" target.  Back-patch to 9.3
(all supported versions).

Branch
------
REL9_5_STABLE

Details
-------
https://git.postgresql.org/pg/commitdiff/d0408c90f423b4a1acfac63ae0f91df83d8cf21a

Modified Files
--------------
Makefile                  | 4 ++++
src/test/regress/Makefile | 5 +++++
2 files changed, 9 insertions(+)