cmake: fix linking against libs in custom prefix

cmake/DPF-plugin.cmake

@@ -188,6 +188,7 @@ function(dpf__build_jack NAME DGL_LIBRARY)
     OUTPUT_NAME "${NAME}")
 
   target_include_directories("${NAME}-jack" PRIVATE ${JACK_INCLUDE_DIRS})
+  target_link_directories("${NAME}-jack" PRIVATE ${JACK_LIBRARY_DIRS})
   target_link_libraries("${NAME}-jack" PRIVATE ${JACK_LIBRARIES})
   link_directories(${JACK_LIBRARY_DIRS})
 endfunction()
@@ -242,6 +243,7 @@ function(dpf__build_dssi NAME DGL_LIBRARY)
       OUTPUT_NAME "${NAME}_ui")
 
     target_include_directories("${NAME}-dssi-ui" PRIVATE ${LIBLO_INCLUDE_DIRS})
+    target_link_directories("${NAME}-dssi-ui" PRIVATE ${LIBLO_LIBRARY_DIRS})
     target_link_libraries("${NAME}-dssi-ui" PRIVATE ${LIBLO_LIBRARIES})
     link_directories(${LIBLO_LIBRARY_DIRS})
   endif()
@@ -347,6 +349,7 @@ function(dpf__add_dgl_cairo)
   target_compile_definitions(dgl-cairo-definitions INTERFACE "DGL_CAIRO" "HAVE_CAIRO")
 
   target_include_directories(dgl-cairo PUBLIC ${CAIRO_INCLUDE_DIRS})
+  target_link_directories(dgl-cairo PRIVATE ${CAIRO_LIBRARY_DIRS})
   target_link_libraries(dgl-cairo PRIVATE dgl-cairo-definitions ${CAIRO_LIBRARIES})
   link_directories(${CAIRO_LIBRARY_DIRS})
 endfunction()