Tested on OS X with brew unlink pkg-config

./autogen.sh
configure.ac:83: error: PKG_PROG_PKG_CONFIG macro not expanded, please install pkg-config
      If this token and others are legitimate, please use m4_pattern_allow.
      See the Autoconf documentation.
autoreconf: /usr/local/Cellar/autoconf/2.69/bin/autoconf failed with exit status: 1

./configure
configure: error: pkg-config not found.

pkg-config isn't required for win32. The fact that it is in some places atm is a bug.

While I generally support making as much as possible optional, I see no value in pkg-config (or pkgconf) being optional.

@luke-jr reason being that it sometimes does more harm than good on Windows. But I suppose at this point we may be over-complicating things by trying to avoid the dependency.

Maybe we'd be better off requiring it everywhere, and just not using it for Windows.

@theuni I do not like requiring it where we do not need it. If we do not use it, it is more difficult to start compiling the source code (one more tool to install/workaround).

If this change makes pkg-config unavailability an error, good, we can change it afterwards.

Or just require and it everywhere, including Windows... only pkgconf problems I'm aware of were fixed years ago.

@luke-jr Yes, this is the status-quo as of now.

Closing. Not needed now after #8314.