llvm: optionally build compiler-rt, libcxx and libunwind as runtimes (#32476)

* llvm: replace +omp_as_runtime with omp=runtime

* llvm: fetch 'libomp-libflags-as-list.patch' from upstream repo

* llvm: replace 'llvm14-hwloc-ompd.patch' with the official fix from upstream repo

* llvm: fix-up for the black reformatting

* llvm: fetch 'constexpr_longdouble.patch' from upstream repo

* llvm: optionally build libcxx as a runtime

* llvm: fetch 'llvm5-sanitizer-ustat.patch' from upstream repo

* llvm: update 'sanitizer-ipc_perm_mode.patch'

* llvm: refactor compiler conflicts when libcxx=project

* llvm: fetch 'llvm_python_path.patch' from upstream repo

* llvm: update comments and condition for 'xray_buffer_queue-cstddef.patch'

* llvm: optionally build compiler-rt as a runtime

* llvm: fetch 'lldb_external_ncurses-10.patch' from upstream repo

* llvm: fetch 'llvm_py37.patch' from upstream repo

* llvm: rename variant 'internal_unwind' to 'libunwind'

* llvm: optionally build libunwind as a runtime

* llvm: extend the list of maintainers

* llvm: allow for explicit '~clang~flang~libomptarget~lldb~omp_debug~z3'

* llvm: fetch 'llvm5-lld-ELF-Symbols.patch' from FreeBSD port repo

* llvm: fetch most of 'missing-includes.patch' from upstream repo and reuse 'llvm-gcc11.patch'

* llvm: regroup patches for missing include directives and drop compiler constraints for them

* llvm: fetch 'llvm-gcc11.patch' from upstream repo

* llvm: fetch 'no_cyclades.patch' from upstream repo

* llvm: update comments and condition for 'no_cyclades9.patch'

* llvm: rename variant 'omp' to 'openmp'

* llvm: constrain and rename variant 'omp_tsan' to 'libomp_tsan'

* llvm: rename variant 'omp_debug' to 'libomptarget_debug'

* llvm: do not apply same patch twice

* llvm: constrain and document the '*-thread.patch' patches

* llvm: document the '~lld+libomptarget' conflict

* llvm: update comments for the 'D133513.diff' patch

share/spack/gitlab/cloud_pipelines/stacks/data-vis-sdk/spack.yaml

@@ -14,7 +14,7 @@ spack:
     llvm:
       require: "@14:"
       # Minimize LLVM
-      variants: ~lldb~lld~internal_unwind~polly~compiler-rt~gold
+      variants: "~lldb~lld~polly~gold libunwind=none compiler-rt=none"
     all:
       require: target=x86_64_v3