Replaces the boolean 'build_libfuzzer' meson option with 'fuzzing_engine'.
This allows reproducing fuzzing test cases on systems without libfuzzer.
Also prevents regressions in the fuzzing test target since it will be
build by default.
wiener_luma_8bpc_c: 326272.1
wiener_luma_8bpc_avx2: 19841.5
Decoding time of first 1000 frames of Chimera-8bit-1920x1080.ivf goes
from 27.471 to 23.558 seconds.
Disabled by default, enabble with `meson -Dbuild_libfuzzer=true -Db_lundef=false ...`.
Fuzz target improved by the paralell work by Thierry Foucu in !138.
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
the tests.
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.
Fix#44
