[libz_all] Add crc32 sandboxing to Capsicum-sandboxed zlib for consistency with libcheri-sandboxed zlib.
[gzip_all] Test script updates.
Add csu_u, containing crt_sb.S. This is in order to insert the hacky fix in invoke() earlier into the CCall landing pad, so that libz_h2 works properly when compiled with -O0.
[csu_u] Add fix for ephemeral caps as previously done in invoke().