Building on macOS 10.14 Mojave

Xcode 10 doesn't build Purr Data for some reason. Go get Command Line Tools (macOS 10.13) for Xcode 9.4.1 on https://developer.apple.com/download/more/.

Seems like there are changes in the locations of the libraries so configure can't find dependencies. Also rumors are that 10.14 stopped supporting anything with -mmacosx-version-min less than 10.9, but by using the old Command Line Tools things are working out just fine.

Wasted a lot of time on this, so I just wrote it down in case anyone upgrades on impulse like me...