ci: use clang18 for msan build #6036

Job	Run time
git_checks	6s
format	30s
el8 (el8, icc, mpich)	5m 58s
ubuntu (ubuntu20.04, gcc8, mpich)	9m 17s
el8 (el8, oneapi, mpich)	5m 56s
ubuntu (ubuntu20.04, gcc9, mpich)	1s
CodeQL (cpp)	5m 59s
ubuntu (ubuntu20.04, gcc10, mpich)	5m 55s
docker (ubuntu-bionic)	6m 7s
ubuntu (ubuntu20.04, clang6, mpich)	5m 57s
ubuntu (ubuntu20.04, clang10, mpich)	5m 57s
windows (win2019, shared, msmpi)	6m 3s
macos (macos-13, xcode14_2, x64, shared, serial)	6m 20s
ubuntu (ubuntu20.04, gcc8, ompi)	1m 28s
windows (win2022, shared, msmpi)	5m 58s
windows (win2022, serial, windows-2022, vs2022)	6m 7s
ubuntu (ubuntu20.04, gcc8, serial)	5m 56s
macos (macos-14, xcode15_4, arm64, shared, serial)	6m 11s
macos (macos-14, xcode15_4, arm64, static, serial)	4m 15s
windows (win2022, static, serial, windows-2022, vs2022)	5m 58s
ubuntu (ubuntu20.04, clang6, ompi)	5m 57s
ubuntu (ubuntu20.04, clang6, serial)	5m 56s
ubuntu (ubuntu20.04, gcc8, serial, static)	1s
ubuntu (ubuntu22.04, rocm, serial, build_only)	1s
ubuntu (ubuntu22.04, gcc11, mpich)	1s
contract	1s
build_and_test	1s
	1h 51m 57s

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