[packaging] Allow using system libraries over 3rd party bundled ones
Working on packaging what will become Inkscape 1.0 for GNU Guix, I noticed the presence of bundled libraries such as libcroco under the src/3rdparty
directory.
I'd like to request that the build system allow choosing system libraries over these bundled libraries, either by default when they are found or through some command line switch.
Also, the source of these libraries appear to be just copied into the project (not tracking the external projects through submodules, for example). Using git submodules for these would improve traceability.
Currently I'm using some custom rewrite rules to unbundle the 3rd party libraries.