Remove autotools build system

[jfowkes]

As per @amontoison suggestion, we should really remove the autotools build system from SPRAL, it is unmaintained, nobody even remotely understands it, and everyone now builds SPRAL with meson which is far easier to maintain.

@AndrewLister-STFC @tyronerees @nimgould let us know your opinions on this.

[tyronerees]

👍 This would be good - I think using something modern would bring lots of benefits.

[kkofler]

One thing the autotools build system currently supports and the meson build system does not is building without OpenMP support. Which (while I realize it is obviously not the development focus of SPRAL) happens to be what we want in our current application (because we run an Ipopt multistart in parallel, so we end up maxing out all CPU cores just fine without parallelizing at the linear solver level – the fact that SPRAL is thread-safe and needs no global mutex, unlike the only other FOSS alternative (MUMPS, which by the way is not designed for sequential solving either), helps a lot there). Though I guess it would not be too hard to add an option, I could probably submit a pull request for that.

[jfowkes]

Thanks for the heads up, I believe you can just pass -Dopenmp=disabled to Meson and it turns off OpenMP?

[kkofler]

I have not tried it yet, but I don't think this currently works. This snippet:

spral/meson.build

Line 97 in 861db06

# OpenMP

just unconditionally adds -fopenmp and -lgomp without checking any option.

[jfowkes]

So it does, we should be able to easily add an option to turn off OpenMP support. @amontoison?

[jfowkes]

@jwnimmer-tri are you guys okay with us removing the autotools build system from SPRAL and just using meson? We wouldn't want to break the Drake tests again.

[jwnimmer-tri]

No problem, thanks. We have our own bazel build for SPRAL, so don't use autotools nor meson.