build

try clang-18 with riscv/sid #516

Job	Run time
linux-glibc-debian-sid-llvm-riscv64	18s
linux-glibc-debian-bookworm-llvm	6m 47s
linux-glibc-debian-bookworm-gcc	5m 31s
linux-glibc-debian-sid-gcc-riscv64	3m 41s
linux-glibc-debian-testing-gcc	5m 42s
linux-glibc-debian-testing-llvm	6m 59s
linux-musl-alpine-gcc	3m 5s
linux-musl-alpine-llvm	21s
linux-musl-debian-bookworm-gcc	5m 12s
linux-musl-debian-bookworm-llvm	6m 20s
linux-musl-debian-sid-gcc-riscv64	23s
linux-musl-debian-sid-llvm-riscv64	19s
linux-musl-debian-testing-gcc	5m 31s
linux-musl-debian-testing-llvm	6m 21s
linux-musl-from-mac	8m 10s
reuse-check	7s
shellcheck	7s
spellcheck	4s
mac-clang	9m 31s
mac-llvm	9m 51s
win-gcc	6m 12s
win-llvm	10m 22s
	1h 40m 54s

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