[Chapel Merge] Explicitly use UTF-8 encoding in 'make spectests'

Branch: refs/heads/master
Revision: 75d4418
Author: mppf
Log Message:

Merge pull request #16608 from mppf/fix-make-spectests

Explicitly use UTF-8 encoding in ‘make spectests’

To avoid errors in some testing configurations that seem to use ASCII by
default.

Allows this command to run:

LC_ALL=C PYTHONUTF8=0 doc/util/extract-rst-tests.py  doc/rst/language/spec/ --output ./test/release/examples/spec

I am not sure what the testing configurations are doing to end up with an
ASCII by default Python, but the code can be adjusted here in any case.

Reviewed by @ben-albrecht - thanks!

Modified Files:
M doc/util/extract-rst-tests.py

Compare: https://github.com/chapel-lang/chapel/compare/49b7834b19d3...75d4418cf628