Fix LLVM easyblock to allow building with multiple versions at once

[Flamefire]

This ensures that the global dicts used as default values are not modified anymore and hence a following build gets a fresh copy.

This avoids failures when building different LLVM versions with conflicting settings.

I also pulled out 2 changes from #3755

1. Rename usepolly to use_polly
2. add a method to CMakeMake to generate a string out of a list suitable for a CMake argument to replace common, error-prone code

Can be tested with easybuilders/easybuild-easyconfigs#23033 which renames the uses of usepolly in easyconfigs and hence also serves as a test case for the fix

The resulting installations should be identical to the ones before

Fixes #3758

[boegel]

lgtm

[boegel]

Test report by @boegel

Overview of tested easyconfigs (in order)

• SUCCESS lit-18.1.2-GCCcore-12.3.0.eb
• SUCCESS LLVM-16.0.6-GCCcore-12.3.0.eb

Build succeeded for 2 out of 2 (1 easyconfigs in total)
node4016.donphan.os - Linux RHEL 9.4, x86_64, Intel(R) Xeon(R) Gold 6240 CPU @ 2.60GHz (cascadelake), 1 x NVIDIA NVIDIA A2, 570.133.20, Python 3.9.18
See https://gist.github.com/boegel/53cae916aa9dc98567fd4b3b090a42a1 for a full test report.

[boegel]

Test report by @boegel

Overview of tested easyconfigs (in order)

• SUCCESS LLVM-16.0.6-GCCcore-12.3.0.eb
• SUCCESS LLVM-18.1.8-GCCcore-13.3.0.eb
• SUCCESS LLVM-20.1.5-GCCcore-13.2.0.eb

Build succeeded for 3 out of 3 (3 easyconfigs in total)
node3512.doduo.os - Linux RHEL 9.4, x86_64, AMD EPYC 7552 48-Core Processor (zen2), Python 3.9.18
See https://gist.github.com/boegel/94236b63251f84dd2cc59773a7e84ef9 for a full test report.

[boegel]

lgtm

also tested extensively via easybuilders/easybuild-easyconfigs#23033

[Flamefire]

Test report by @Flamefire

Overview of tested easyconfigs (in order)

• SUCCESS LLVM-19.1.7-GCCcore-13.3.0.eb
• SUCCESS LLVM-20.1.5-GCCcore-13.3.0.eb
• FAIL (build issue) LLVM-18.1.8-GCCcore-13.3.0.eb (partial log available at https://gist.github.com/Flamefire/bad745c1f8244e2e777d6964567101e0)

Build succeeded for 2 out of 3 (3 easyconfigs in total)
n1623 - Linux RHEL 8.9 (Ootpa), x86_64, Intel(R) Xeon(R) Platinum 8470 (sapphirerapids), Python 3.9.18
See https://gist.github.com/Flamefire/19e408b5963fb8f4c2bc36ec69302044 for a full test report.

[Flamefire]

Test report by @Flamefire

Overview of tested easyconfigs (in order)

• SUCCESS LLVM-19.1.7-GCCcore-13.3.0.eb
• SUCCESS LLVM-20.1.5-GCCcore-13.3.0.eb
• FAIL (build issue) LLVM-18.1.8-GCCcore-13.3.0.eb (partial log available at https://gist.github.com/Flamefire/90c8f0864b9713dfb2189f523d92e59b)

Build succeeded for 2 out of 3 (3 easyconfigs in total)
c121 - Linux AlmaLinux 9.4, x86_64, AMD EPYC 9334 32-Core Processor (zen4), 4 x NVIDIA NVIDIA H100, 560.35.03, Python 3.9.18
See https://gist.github.com/Flamefire/25e80555d062bd53ff6f5df09d132733 for a full test report.

[boegelbot]

Test report by @boegelbot

Overview of tested easyconfigs (in order)

• SUCCESS LLVM-18.1.8-GCCcore-13.3.0-minimal.eb
• SUCCESS LLVM-20.1.5-GCCcore-13.3.0.eb

Build succeeded for 2 out of 2 (2 easyconfigs in total)
jsczen3c3.int.jsc-zen3.fz-juelich.de - Linux Rocky Linux 9.5, x86_64, AMD EPYC-Milan Processor (zen3), Python 3.9.21
See https://gist.github.com/boegelbot/59a2479b3477c85355da2b7d2f848bca for a full test report.

[Flamefire]

Test report by @Flamefire

Overview of tested easyconfigs (in order)

• SUCCESS LLVM-19.1.7-GCCcore-13.3.0.eb
• SUCCESS LLVM-20.1.5-GCCcore-13.3.0.eb
• SUCCESS LLVM-18.1.8-GCCcore-13.3.0.eb

Build succeeded for 3 out of 3 (3 easyconfigs in total)
i7108 - Linux Rocky Linux 8.9 (Green Obsidian), x86_64, AMD EPYC 7702 64-Core Processor (zen2), Python 3.9.18
See https://gist.github.com/Flamefire/161a4699f2ef3d3eaa52c14088fad01e for a full test report.