build: refactor imageprovider makefile a bit
build: refactor imageprovider makefile a bit

Similar to commit 5a941ac479883bef11bd9ada65b07fafafff2ad1
([build] add missing include path for builddir != srcdir)

sklnet/DirectFB,sklnet/DirectFB,kaostao/directfb,deniskropp/DirectFB,djbclark/directfb-core-DirectFB,lancebaiyouview/DirectFB,Distrotech/DirectFB,kaostao/directfb,kaostao/directfb,kevleyski/DirectFB-1,DirectFB/directfb,DirectFB/directfb,lancebaiyouview/DirectFB,djbclark/directfb-core-DirectFB,sklnet/DirectFB,kevleyski/directfb,dfbdok/DirectFB1,jcdubois/DirectFB,kevleyski/DirectFB-1,mtsekm/test,kevleyski/directfb,djbclark/directfb-core-DirectFB,lancebaiyouview/DirectFB,mtsekm/test,djbclark/directfb-core-DirectFB,kevleyski/DirectFB-1,deniskropp/DirectFB,kevleyski/directfb,deniskropp/DirectFB,lancebaiyouview/DirectFB,jcdubois/DirectFB,DirectFB/directfb,mtsekm/test,deniskropp/DirectFB,dfbdok/DirectFB1,dfbdok/DirectFB1,kevleyski/directfb,kevleyski/DirectFB-1,sklnet/DirectFB,jcdubois/DirectFB,Distrotech/DirectFB,Distrotech/DirectFB