Minor patches to TBB Windows build for compatibility with RTools make

[andrjohns]

Summary

This PR applies some minor changes to the TBB's build rules on Windows so that it can be compiled with the version of make bundled with RTools - users will no longer need to additionally install mingw32-make on windows.

These changes are based on RcppParallel's changes.

I've run a GHA workflow which shows that the Math library & TBB successfully build with these changes under RTools40, RTools42, and RTools43 - without needing to install any additional packages

Tests

N/A - existing tests should still pass, testing workflow already run to confirm successful build

Side Effects

N/A

Release notes

Updated TBB Windows build rules for compatibility with RTools make

Checklist

• Copyright holder: Andrew Johnson

  The copyright holder is typically you or your assignee, such as a university or company. By submitting this pull request, the copyright holder is agreeing to the license the submitted work under the following licenses:
  - Code: BSD 3-clause (https://opensource.org/licenses/BSD-3-Clause)
  - Documentation: CC-BY 4.0 (https://creativecommons.org/licenses/by/4.0/)

• the basic tests are passing

  • unit tests pass (to run, use: ./runTests.py test/unit)
  • header checks pass, (make test-headers)
  • dependencies checks pass, (make test-math-dependencies)
  • docs build, (make doxygen)
  • code passes the built in C++ standards checks (make cpplint)

• the code is written in idiomatic C++ and changes are documented in the doxygen

• the new changes are tested

[andrjohns]

I've also left the existing usage of mingw32-make in the header tests workflow, to show that the changes won't break any existing configuration

[andrjohns]

@WardBrian Any chance we could sneak this through in the 2.34 release? It would help simplify the windows setup steps (only need to set PATH now)

@wds15 would you happen to remember the POSIX issues that led to the mingw32-make requirement? I haven't experienced any build or runtime issues yet, but want to double-check that I'm not missing anything

[andrjohns]

Could we do this in the code that calls the TBB makefiles, rather than needing to modify them here? (I don't mind the extra /s later on)

If so, could we provide some alternative variable like WINDOWS_HAS_SH or something?

@WardBrian good call! I've updated the makefiles to first do a check for the presence of sh, which can be overridden by manually setting WINDOWS_HAS_SH

[WardBrian]

Changes look good now, thanks!

As for this in the 2.34 release, I'm torn. Calling the fact that make didn't work before a bug would allow it, but I also would not mind more time for testing on something like this.

@rok-cesnovar thoughts?

[rok-cesnovar]

First of all, this is awesome. Not requiring mingw32-make is a huge huge win!

But cmdstan scripts still require it right now and I think we would need to clean up the Cmdstan makefiles, cleanup docs and installation instructions before the release. We could do that, but it feels like it would be a bit rushed to me.

And yeah, more testing time would be helpful as well. Asking Windows users to test the RC because of a somewhat big change would be helpful as well.

The only other option is making an RC2 and prolonging the freeze period.

[andrjohns]

First of all, this is awesome. Not requiring mingw32-make is a huge huge win!

But cmdstan scripts still require it right now and I think we would need to clean up the Cmdstan makefiles, cleanup docs and installation instructions before the release. We could do that, but it feels like it would be a bit rushed to me.

And yeah, more testing time would be helpful as well. Asking Windows users to test the RC because of a somewhat big change would be helpful as well.

The only other option is making an RC2 and prolonging the freeze period.

Ah yeah good point. This change isn't particularly urgent, better to play it safe

[WardBrian]

Agreed @rok-cesnovar, this is a great change! I had always suspected that the issues with make and TBB were surface-level due to the makefiles rather than something fundamental, but I never had the knowledge or motivation to dig too deeply.

Getting the build system out of our way is also the current barrier to using the Microsoft compilers (or at least Clang-for-MSVC) for Stan, which is a goal of mine. One day

[wds15]

@andrjohns I only recall that make simply did not do it and the mingw thing did it.... that's when I stopped looking for further "why". It would be great to now require any more the mingw thinggy.

[WardBrian]

@andrjohns would you mind looking into what needs to be changed in the stan and cmdstan repos?