Respect CXX environment variable for C++ compiler selection#1

Copilot wants to merge 3 commits intomainmaresb/pytensor:mainfrom

copilot/fix-35db4a4f-9436-4238-92e7-cf948d8e4ed4maresb/pytensor:copilot/fix-35db4a4f-9436-4238-92e7-cf948d8e4ed4Copy head branch name to clipboard