[Chapel Merge] Use LLVM by default if LLVM is available either as

Branch: refs/heads/master
Revision: 092cf55
Author: daviditen
Log Message:

Merge pull request #17079 from daviditen/llvm-on-by-default

Use LLVM by default if LLVM is available either as system or bundled

[reviewed by @mppf]

Change the default to be the equivalent of using the --llvm flag if LLVM is
available. The C backend can still be used by either setting
CHPL_LLVM_BY_DEFAULT=0 or using the --no-llvm flag.

Update nightly testing script to stop adding -compopts --llvm for LLVM testing
and to add -no-llvm option that adds -compopts --no-llvm.

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

Modified Files:
M compiler/main/driver.cpp

M util/cron/nightly

Compare: https://github.com/chapel-lang/chapel/compare/216b136c3373...092cf5562e37