LLVM 15.0.5 build fails on A64FX

[bedroge]

See #1177, the build failed with the following error:

/tmp/eb-2llwp9cq/eb-fxhc1oex/cck4kRMa.s: Assembler messages:
/tmp/eb-2llwp9cq/eb-fxhc1oex/cck4kRMa.s:18047: Error: immediate offset out of range 0 to 31 at operand 3 -- `st1b z2.d,p0,[z0.d,#88]'
make[2]: *** [lib/Transforms/Utils/CMakeFiles/LLVMTransformUtils.dir/build.make:289: lib/Transforms/Utils/CMakeFiles/LLVMTransformUtils.dir/CodeLayout.cpp.o] Error 1
make[2]: *** Waiting for unfinished jobs....
make[2]: Leaving directory '/tmp/eessibot/easybuild/build/LLVM/15.0.5/GCCcore-12.2.0/easybuild_obj'
make[1]: *** [CMakeFiles/Makefile2:10253: lib/Transforms/Utils/CMakeFiles/LLVMTransformUtils.dir/all] Error 2
make[1]: *** Waiting for unfinished jobs....

Compiling it with optarch=march=armv8.2-a works though, so we'll add that to our hooks.

[bedroge]

Rust 1.65.0 actually failed due to that same issue, as it includes LLVM 15. We worked around that by bumping Rust to 1.75.0 and adding an dummy module file for 1.65.0 that prints an error. We could revisit this and still try to (re)build Rust 1.65.0 with the same optarch flag.

[bedroge]

A fix that changes optarch for both LLVM and Rust has been implemented in EESSI/software-layer-scripts#97.