meta-efl/screenshot: fix building with current gettext/auto*

Current auto*/gettext stopped substituting @MKINSTALLDIRS@ variable
which is necessary in screenshot/po/Makefile. Fix that by calling
AM_MKINSTALLDIRS manually.

Signed-off-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>