build-llvm: Bump to LLVM 18.1.2 #1057

Job	Run time
prepare	10s
linux	2h 13m 13s
macos	2h 54m 45s
linux-asserts	0s
msys2 (mingw64)	2h 7m 9s
msys2 (clang64)	1h 45m 13s
linux-test-cross-build-ffmpeg	0s
linux-cross-windows (i686, ucrt)	2h 55m 47s
linux-cross-aarch64	2h 17m 56s
linux-cross-windows (x86_64, ucrt)	3h 1m 18s
linux-cross-windows (armv7, ucrt)	2h 52m 52s
linux-cross-windows (aarch64, ucrt)	2h 54m 32s
test-openmp	0s
test-compiler-rt	0s
test-libcxx	0s
test-ffmpeg	0s
test-toolchain (x86_64)	1m 54s
test-toolchain (i686)	2m 4s
upload-nightly	0s
	23h 6m 53s

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