Simplify the flatpak build script

Author: kovzol

qt/io.github.kovzol.bibref.yaml

@@ -33,14 +33,15 @@ modules:
       - -DBUILD_SHARED_LIBS=ON
       - -UPROJECT_SOURCE_DIR
       - -DPROJECT_SOURCE_DIR=/app/share/bibref-qt
+    # The cmake machinery will put the required databases in $XDG_DATA_HOME (if it is set).
+    # By setting that value we put the database to /app/tmp/.sword temporarily
+    # and later we copy it to /app/share/sword in the post-install step:
     build-options:
       env:
         XDG_DATA_HOME: /app/tmp
     sources:
       - type: archive
         url: https://github.com/kovzol/bibref/archive/85f8636bd3ff427c6678022017397bfb42785742.zip
         sha256: f98542b0f91323627e77bb7839252056c3055c364742d12578a505335367e27d
-  - name: finalize
-    buildsystem: simple
-    build-commands:
+    post-install:
       - mv /app/tmp/.sword/* /app/share/sword