Replace usepolly to use_polly in LLVM easyconfigs

[Flamefire]

requires:

• Fix use of CUDA CCs in LLVM easyblock and cleanup  easybuild-easyblocks#3755

(created using eb --new-pr)

[Flamefire]

Test report by @Flamefire
Using easyblocks from PR(s) easybuilders/easybuild-easyblocks#3755
FAILED
Build succeeded for 21 out of 25 (17 easyconfigs in total)
i7176 - Linux Rocky Linux 8.9 (Green Obsidian), x86_64, AMD EPYC 7702 64-Core Processor (zen2), Python 3.8.17
See https://gist.github.com/Flamefire/c48b3f43a333c37e3f533996399e5007 for a full test report.

[Thyre]

Failures caused by easybuilders/easybuild-easyblocks#3758

[Flamefire]

Test report by @Flamefire
Using easyblocks from PR(s) easybuilders/easybuild-easyblocks#3755
SUCCESS
Build succeeded for 3 out of 3 (1 easyconfigs in total)
n1149 - Linux RHEL 8.9 (Ootpa), x86_64, Intel(R) Xeon(R) Platinum 8470 (sapphirerapids), Python 3.9.18
See https://gist.github.com/Flamefire/8860772f42707a8e25a92632075d89b0 for a full test report.

[Flamefire]

Test report by @Flamefire
Using easyblocks from PR(s) easybuilders/easybuild-easyblocks#3755
FAILED
Build succeeded for 19 out of 20 (17 easyconfigs in total)
n1418 - Linux RHEL 8.9 (Ootpa), x86_64, Intel(R) Xeon(R) Platinum 8470 (sapphirerapids), Python 3.9.18
See https://gist.github.com/Flamefire/40acefdd28e2b7261d521605e7a5d7f3 for a full test report.

Failures in LLVM-18.1.8-GCCcore-13.3.0.eb look unrelated:

• a few segmentation faults
• LEAK sanitizer not detecting leaks
• CommandLine Error: Option 'debug-counter' registered more than once! (?)
• MemorySanitizer-Unit fails on __msan_test_shadow
• Some "UTC" vs "GMT" mismatches

So I guess Sapphire Rapids and possibly the libc is just not really supported for LLVM 18

[Flamefire]

Test report by @Flamefire
Using easyblocks from PR(s) easybuilders/easybuild-easyblocks#3755
SUCCESS
Build succeeded for 17 out of 17 (17 easyconfigs in total)
i7034 - Linux Rocky Linux 8.9 (Green Obsidian), x86_64, AMD EPYC 7702 64-Core Processor (zen2), Python 3.8.17
See https://gist.github.com/Flamefire/2841dcdf522caa872ed5fe9750134837 for a full test report.