`./configure --with-macosx-deployment-target=` doesn't work
This is tested on HEAD with OS X 10.8.2 using Xcode 4.5.2.
Any version X in
./configure --with-macosx-deployment-target=X results in configure failing with:
checking Mac OS X deployment target... configure: error: Unknown deployment target X
Examining configure reveals that the option appears to have bit rotted since SDK paths all point to "/Developer/...", whereas these days it should point inside the Xcode application bundle.
The SDK path should be gotten by appending "/Platforms/MacOSX.platform/Developer/SDKs/MacOSX<version>.sdk" to the output of
xcode-select --print-path, resulting in something like "/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.8.sdk".
If continuing support for systems with old versions of Xcode is desirable, we should first try generating a path using
xcode-select, and if that fails we should fall back to trying "/Developer/...".