Tidy up shared mode htslib_library_dirs
Tidy up shared mode htslib_library_dirs

Remove distutils_dir_name() and "build/DISTUTILS_DIR/pysam", as this
directory path has been incorrect since setuptools v62.1.0 (see #1113).
In practice, the correct "build/.../pysam" directory is automatically
added by build_ext anyway.

Also remove "pysam", as a duplicate is added in common_options anyway.

Probably "." is unnecessary too (no libraries are built in the top-level
directory), but more testing is needed with `setup.py developer` before
changing that.

pysam-developers/pysam,pysam-developers/pysam,pysam-developers/pysam,pysam-developers/pysam