postgresql: Fix packaging of static libraries

This patch fixes the following QA issue:

,----[ Fragment of build error log ]
| ...
| ERROR: QA Issue: non -staticdev package contains static .a library:
|   libecpg-dev path '/work/.../packages-split/libecpg-dev/usr/lib/libpgtypes.a'
| ...
`----

Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>
Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>