Configure script output doesn't mention CXX

Bug report

Bug description:

I was having trouble getting test_cppext to pass on both my Mac and Ubuntu laptops. (Oddly enough, while running that test in isolation, it passed.) It succeeded on my Raspberry Pi. Trying to figure out what I'd done wrong, I noticed that I was setting CC=clang except on the Pi, but wasn't specifying a C++ compiler. I don't know what logic configure uses to set the C++ compiler if CC is set, but figured I could probably override it. ./configure --help doesn't mention anything C++-related, but CXX is referenced in configure.ac.

Thinking I'd hit on the solution by specifying CXX=clag++, I tried again. Alas, I still get the test_cppext failure and will continue to hunt for that problem. Nevertheless, it seems to me that ./configure --help should mention the CXX variable.

CPython versions tested on:

CPython main branch

Operating systems tested on:

macOS, Linux

Linked PRs

• gh-157046

El issue apunta a configure.ac y ./configure --help; empieza leyendo el manejo de CXX en configure.ac y comprobando la salida de ayuda generada. Se considera terminado cuando la salida de ayuda documenta CXX; el PR gh-157046 ya está enlazado, así que comprueba su estado antes de empezar.