build: switch to using LLVM 17.x for macOS builds
Summary:
We need LLVM 17.x so that lld has -fixup_chains.
Backport of core#28880.
Depends on D17254.
Test Plan: Run the osx guix build.
Reviewers: #bitcoin_abc, PiRK
Reviewed By: #bitcoin_abc, PiRK
Differential Revision: https://reviews.bitcoinabc.org/D17247