libomp @19.1.2 fails to configure on < 10.15

[jmroot (Joshua Root)]

e.g. ​https://build.macports.org/builders/ports-10.14_x86_64-builder/builds/221222/steps/install-port/logs/stdio

CMake Error at /opt/local/share/cmake-3.29/Modules/FindPackageHandleStandardArgs.cmake:230 (message):
  Could NOT find Python3 (missing: Python3_EXECUTABLE Interpreter)

[aeiouaeiouaeiouaeiouaeiouaeiou]

Caused by getting rid of building via Perl: ​https://github.com/llvm/llvm-project/commit/88dae3d5d0230747f3cbabdde9ac5ae9e5dc3f8d

Now we need to add a dependency on Python as in the ​LLVM port.

[jmroot (Joshua Root)]

Make sure not to use a python port that has libomp in its recursive deps. C11 is needed for python 3.11 and later which means a clang dependency on older systems.

[ryandesign (Ryan Carsten Schmidt)]

clang ports depend on libomp; with libomp broken, ports that need a newer clang can't build either.

[eborisch (Eric A. Borisch)]

Ugh. This is going to get ugly, isn’t it. We can just revert back to previous version for now? Thoughts?

[jmroot (Joshua Root)]

Use python310 for now? We might end up needing some new bootstrap port somewhere to break the cycle.

[jmroot (Joshua Root)]

In 745ec6b54b020e8feacdeec212b224d89c852660/macports-ports (master):

libomp: add python310 build dep

Also restrict perl5 dep to older version.

Fixes: #71149

[kencu (Ken)]

worth considering: no clang actually needs libomp as a dep

[eborisch (Eric A. Borisch)]

Replying to jmroot:

In 745ec6b54b020e8feacdeec212b224d89c852660/macports-ports (master):

libomp: add python310 build dep

Also restrict perl5 dep to older version.

Fixes: #71149

Thank you! On my list to get to today, but you beat me to it.

[eborisch (Eric A. Borisch)]

Replying to kencu:

worth considering: no clang actually needs libomp as a dep

Certainly worth considering. Ports/variants that need it can always say so, and it would minimize the fallout from any future issues to those ports that actually need it.