[Chapel Merge] Set the encoding when calling check_output in the

Branch: refs/heads/master
Revision: d6e5d0a
Author: lydia-duncan
Log Message:

Merge pull request #16617 from lydia-duncan/fixRpmBuildPython

Set the encoding when calling check_output in the build_configs script
[reviewed by @mppf]

Without this change, the returned output was bytes rather than str, which lead
to issues with concatenating a str to it later in the file.

./util/buildRelease/test_rpm_module.bash builds a module that can be loaded
and used to build hello.chpl (which runs appropriately) with this change.

Modified Files:
M util/build_configs/build_configs.py

Compare: https://github.com/chapel-lang/chapel/compare/6468acdcbcb8...d6e5d0ab33e8