How to force linking against a static library when the dynamic version exists in default search path ?

If you want to link against a static version of a library that already exists on the Mac in a standard search path like /usr/lib but in shared version (like libxml2.dylib) ?
In your link options, be sure that the path to the static version is in the Library search paths list and then add -Wl,-search_paths_first in the Other Link Flags.