package/gstreamer1/gstreamer1-editing-services: fix static build

Fix static build with gstreamer1-editing-services in version 1.17.1 and
above

Fixes:
 - http://autobuild.buildroot.org/results/2a528a1185644f5b23d26eb3f2b342e99aa1e493

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>