5763b232e6 ci: return to using Ubuntu 22.04 in MSAN jobs (fanquake)
d3cbcbf626 ci: compile clang and compiler-rt in MSAN jobs (fanquake)
796bd1d0d1 ci: use LLVM 16.0.4 in MSAN jobs (fanquake)
883bc9f561 ci: remove extra CC & CXX from MSAN jobs (fanquake)
2d4f4b8f29 ci: standardize custom libc++ usage in MSAN jobs (fanquake)
Pull request description:
This reworks the MSAN CIs, to first compile Clang and compiler-rt (using GCC 12), and then, compile an MSAN instrumented libc++ using the just-built Clang 16. This fixes the `native_fuzz_with_msan` job, working around https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1005341, by not using the Debian provided Clang/LLVM.
Also included are changes to streamline how we use our "custom libc++", according to upstream: https://releases.llvm.org/16.0.0/projects/libcxx/docs/UsingLibcxx.html#using-a-custom-built-libc, as well as other minor cleanups in the CI configs.
An example job is currently running in the qa-assets repo: https://github.com/bitcoin-core/qa-assets/pull/129 (https://cirrus-ci.com/task/4632561431871488).
ACKs for top commit:
dergoegge:
utACK 5763b232e6
Tree-SHA512: 4f2a6e0b796bb1830b8346dd1e55eaa86a79037b8b4f16a336c1e29f4fc460acca2ecba076635459370bcbb4009333cb79d27ef1521c1fb5db7599cd5bdf558c
8a972813ba