[Chapel Merge] Consider cray-cs as cross-compiling

Branch: refs/heads/master
Revision: a9d4117
Author: ronawho
Log Message:

Merge pull request #16335 from ronawho/cray-cs-cross-compile

Consider cray-cs as cross-compiling

[reviewed by @gbtitus]

Cray CS login and compute nodes can have different ISAs so consider
them as cross-compiling.

Resolves https://github.com/cray/chapel-private/issues/1262

This makes a few other improvements to our cross-compiling logic
while I was changing things.

It removes vestiges of target platform cross compilation support. We
used to experimentally support arm cross-compilation by specifying
CHPL_TARGET_PLATFORM=aarch64, but that was for a prototype system.
Most of that was removed in #11905, but this was left. I don’t think
it has any purpose anymore, so remove it.

If we support a general cross compiling mechanism in the future I
suspect it will be with CHPL_ARCH, not CHPL_PLATFORM#11903

This also switches from using uname -m to CHPL_TARGET_ARCH for
specifying the third-party ./configure --host

When we’re cross-compiling for Cray’s in our third-party scripts we
throw --host in order to tell configure what type of system the
code will be executing on (note that configure --host is backwards
from our notion of host vs. target.)

Previously, we were just using uname -m, which gives you the host
architecture and on crays the login and compute nodes have to be the
same architecture so this was safe. However, since that work was done
we added a CHPL_{HOST,TARGET}_ARCH variable so we can just use that
instead of computing uname. And here we’re switching from using the
host arch to the target arch since it’s what configure is looking
for. In the cray case they currently have to be the same, but that
might not be true in the future.

Modified Files:
M third-party/gmp/Makefile
M third-party/hwloc/Makefile
M third-party/jemalloc/Makefile
M third-party/libfabric/Makefile
M third-party/qthread/Makefile
M util/chplenv/chpl_compiler.py
M util/chplenv/chpl_launcher.py
M util/chplenv/chpl_platform.py

Compare: https://github.com/chapel-lang/chapel/compare/19dab8202cc0...a9d411710925