[Chapel Merge] Fix problem running 'make' with CC and CXX set

[chapelhpcBot]

Branch: refs/heads/main
Revision: 4112d47eae48cbb9b8dbdcf934f4e7f5822f3835
Author: mppf
Link: Fix problem running 'make' with CC and CXX set by mppf · Pull Request #21985 · chapel-lang/chapel · GitHub
Log Message:
Fix problem running 'make' with CC and CXX set (#21985)

This PR is intended to resolve the build issue discussed in

[1.30] Configuration and Link errors when building, on system where 1.29 previously worked

I've been able to reproduce but I've also exported CC=clang and CXX=clang++ This seems to be needed in order to trigger the problematic behavior. I can reproduce the issue on an Ubuntu Jammy container, but if I remove these, the problem goes away. Why are you setting these variables? Are you trying to build the compiler itself with clang? Or do you want the compiler to work with clang when using the C backend? You can use printchplenv --all to see some of the hidden settings that seem to b…

When building Chapel with something like CC=clang CXX=clang++ make,
several things were going wrong:

1. There was an error from printchplenv
2. That error did not stop the build & later there were linker errors

Why was there an error at all? it was this sequence of events:

• the Makefile invoking cmake set CMAKE_C_COMPILER and
  CMAKE_CXX_COMPILER based on CHPL_MAKE_HOST_CC etc to communicate this
  setting to cmake (so cmake does not infer it based upon CC or use its
  favorite compiler)
• the cmake script invoked printchplenv while setting CHPL_HOST_CC and
  CHPL_HOST_CXX in the environment (so that printchplenv will be
  considering the same configuration that cmake is using)
• printchplenv supports inferring CHPL_HOST_COMPILER from CC and
  CXX but not from CHPL_HOST_CC and CHPL_HOST_CXX. So, it failed,
  because the default value CHPL_HOST_COMPILER=gnu was inconsistent with
  CHPL_HOST_CC=clang / CHPL_HOST_CXX=clang++.

This PR:

• It adjusts the cmake script to check for the return code from
  printchplenv and fail with an error if it is nonzero.
• Enables inferring CHPL_HOST_COMPILER from CHPL_HOST_CC /
  CHPL_HOST_CXX
• Enables inferring CHPL_TARGET_COMPILER from CHPL_TARGET_CC /
  CHPL_TARGET_CXX (but this does not happen when LLVM would be the
  default or when using a PrgEnv).

An alternative solution to the issue of inferring CHPL_HOST_COMPILER
would be to pass it as an environment variable from make to cmake
and from cmake to printchplenv.

Reviewed by @arezaii - thanks!

• verified that CC=clang-14 CXX=clang++-14 make works on an Ubuntu
  22.10 system where it did not work before
• full local testing

Compare: Comparing b70551a006503b4c41ed40cd167e40ca8fe81542...7fd061595cc11b04e00d54288e9480655ec8e97d · chapel-lang/chapel · GitHub

Diff:
M CMakeLists.txt
M util/chplenv/chpl_compiler.py
https://github.com/chapel-lang/chapel/pull/21985.diff