Add LD_LIBRARY_PATH to finish-args

This used to come hardcoded from flatpak-module-tools, but was removed
in flatpak-module-tools 0.11.2. This commit moves it here so that we
don't lose LD_LIBRARY_PATH.

See https://bodhi.fedoraproject.org/updates/FEDORA-FLATPAK-2020-30fe5a648b

container.yaml

@@ -9,9 +9,11 @@ flatpak:
     component: flatpak-sdk
     branch: f30
     runtime: org.fedoraproject.Platform
+    end-of-life: Fedora 30 runtime is no longer supported.
     finish-args: >
         --env=GI_TYPELIB_PATH=/app/lib64/girepository-1.0
         --env=GST_PLUGIN_SYSTEM_PATH=/app/lib64/gstreamer-1.0:/usr/lib64/gstreamer-1.0
+        --env=LD_LIBRARY_PATH=/app/lib64
         --env=XDG_DATA_DIRS=/app/share:/usr/share:/usr/share/runtime/share:/run/host/share
     cleanup-commands: |
         touch -d @0 /usr/share/fonts /usr/share/fonts/*