Fix for Issue #1413 (cherry-pick #179 to release_18x) (#185)

PGMATH has AVX512 runtime functions and can be executed only when the application is compiled
in avx512 mode. The VecFuncs.def has no information about the TargetOptions and avx512 functions
are selected even in avx2 mode. This issue is fixed by creating separate table for AVX512 functions
and using them only when avx512 mode is specified.

[workflows] Upgrade GitHub runner to macOS-13

GitHub has stopped supporting macOS-11, causing our workflows to wait
indefinitely for an unavailable runner.

[workflows] Fix typo in pre-compile_llvm.yml; NFC

[workflows] Update GitHub actions to use modern tools

Cherry-pick patches from release_17x, in order to build the release_16x branch
of classic-flang-llvm-project and flang with GCC 12 and Clang 14/15
on Ubuntu 22.04. This squashes together the following commits:

    e698fc8 [workflows] Update GitHub actions to use modern tools
    6aeab31 [workflows] Fix GitHub action bugs
    77979af [workflows] Fix typo in pre-compile_llvm.yml; NFC

The workflows in the flang repository test both release_16x and release_17x,
and keeping the workflows consistent in these classic-flang-llvm-project
branches simplifies the flang workflows.

Add Flang include directory to MSVC toolchain

script: update llvm build script

* Native Ninja is already available for Windows on ARM,
so we can use it on both Windows platform.

* Introduced a new '-i' build option to trigger whether
the user wants to install LLVM or not. Previously the script relies
on install_prefix option which was wrong approach.
In this case we still could not defer the install for a later time
if install directory was set.
With this change the python build script will be consistent
with official bash script.

[workflows] Delete misleading pull request template

Upstream llvm-project repository does not accept pull requests, but our fork does.

Let /dev/null to be an input file.

Make fortran mode when an input is '-' character indicating stdin.
Make temporary file and make /dev/stdin an input to flang1.
Test files for this change also added- separate one for windows and linux.

[DebugInfo] Enhance DIImportedEntity to accept children entities (#93)

New field `elements` is added to '!DIImportedEntity', representing
list of aliased entities.
This is needed to dump optimized debugging information where all names
in a module are imported, but a few names are imported with overriding
aliases.

Reviewed By: dblaikie

Differential Revision: https://reviews.llvm.org/D109343

Pass to flang2 the MSVC libraries to be linked to