Due to bugs in meson the approach with the intermediate static library
for tests does not work very well, see #44. Therefore this commits
removes that helper library and instead uses extract_all_objects for
Due to the removal of the static helper library, it means we can no
longer force static linking for dav1d tool on windows which means that
when building a shared library the dav1d.exe will not be runnable in
the build directory again.