We're still (see e0e567a106, e0e567a106) working on replacing use of the
deprecated distutils. This commit just makes configure print out the results
of different ways of determining the include path. Hopefully this will help us
to find a way to transition away from distutils without turning the buildfarm
red for prolonged amounts of time.
Discussion: https://postgr.es/m/20220124025301.qu36x44w6m67cnap@alap3.anarazel.de
f032f63e72