Update LLVM version with fix for elided branches coverage

[sasdf]

Update LLVM version with single-byte coverage fix from PR:

• [InstrProf] Fix single byte counters for elided branches llvm-project#5

These changes are specific to coverage builds and remain compatible with the current compiler.

[sasdf]

@luismarques PTAL

Please also help us tagging the commit and triggering a new release after merging.

Thanks!

[luismarques]

@luismarques PTAL

Please also help us tagging the commit and triggering a new release after merging.

Thanks!

I'm away from my desk (bank holiday) but I'll try to tag a release later tonight or tomorrow morning.

[luismarques]

https://github.com/lowRISC/lowrisc-toolchains/actions/runs/15594905152 (running)

[luismarques]

Done: https://github.com/lowRISC/lowrisc-toolchains/releases/tag/20250611-1
I'll update the release notes later.