[Chapel Merge] Improve the error message when CC/CXX conflict

Branch: refs/heads/main
Revision: 2f5c385
Author: ronawho
Log Message:

Merge pull request #18056 from ronawho/improve-conflicting-comp-family-error

Improve the error message when CC/CXX conflict

[reviewed by @mppf]

Improve the chplenv error message when we can't infer the compiler
family from CC/CXX. This can be fixed by either changing CC/CXX or
manually setting CHPL_HOST_COMPILER/CHPL_TARGET_COMPILER

Modified Files:
M util/chplenv/chpl_compiler.py

Compare: https://github.com/chapel-lang/chapel/compare/b5e8c96c830d...2f5c385d6cf8