Not used anymore.

zlib cannot be built out-of-tree, and previously, we were building in
the "src" directory, not in the "build" directory.  The
make_build_path() return value was unused.

Fixes a bug that occurs when runing "build.py" from inside the
"win32" directory.

Fixes in-tree build when the script is called as "win32/build.py"
and not "./win32/build.py".

Allow multiple targets to share a library directory tree.

These do not require GLib anymore.

Due to security vulnerabilities.

Allow library auto-detection without pkg-config.

Finally, MPD runs on Android.  For some small value of "runs".  Very
much work left, too much to describe.