[Chapel Merge] Remove deprecated environment settings from usingc

Branch: refs/heads/main
Revision: 439978c
Author: daviditen
Log Message:

Merge pull request #18382 from daviditen/chplenv-doc-updates

Remove deprecated environment settings from usingchapel/chplenv doc

[reviewed by @dlongnecke-cray]

Remove mentions of settings of the form CHPL_LLVM=llvm that were replaced
with CHPL_LLVM=bundled from the chplenv document.

Add a mention of defaulting to CHPL_LLVM=unset if none of the other cases

Signed-off-by: David Iten daviditen@users.noreply.github.com

Modified Files:
M doc/rst/usingchapel/chplenv.rst

Compare: https://github.com/chapel-lang/chapel/compare/b6a5cded6ab3...439978c6c092