Install QtDesigner plugin

and clean assembly build flag since the abandoned module was removed from codebase

PKGBUILD

@@ -86,11 +86,11 @@ build() {
     -D BUILD_FLAT_MESH=ON \
     -D BUILD_MESH_PART=ON \
     -D BUILD_SHIP=ON \
-    -D BUILD_ASSEMBLY=ON \
     -D BUILD_COMPLETE=ON \
     -D BUILD_JTREADER=OFF \
     -D BUILD_PLOT=ON \
     -D BUILD_CLOUD=OFF \
+    -D BUILD_DESIGNER_PLUGIN=ON \
     -D CMAKE_BUILD_TYPE=None \
     -D CMAKE_C_FLAGS="${CFLAGS} -fPIC -w" \
     -D CMAKE_CXX_FLAGS="${CXXFLAGS} -fPIC -w" \