build-llvm: Bump to LLVM 19.1.6 #1475

Job	Run time
prepare	8s
linux	3h 3m 8s
macos	2h 45m 35s
msys2 (mingw64)	2h 13m 9s
linux-asserts	0s
msys2 (clang64)	1h 50m 42s
linux-test-cross-build-ffmpeg	0s
linux-cross-aarch64	3h 15m 53s
linux-cross-windows (i686, ucrt)	3h 10m 17s
linux-cross-windows (x86_64, ucrt)	3h 9m 44s
linux-cross-windows (armv7, ucrt)	3h 7m 14s
linux-cross-windows (aarch64, ucrt)	3h 7m 7s
test-ffmpeg	0s
test-openmp	0s
test-compiler-rt	0s
test-libcxx	0s
test-toolchain (x86_64)	2m 15s
test-toolchain (i686)	2m 15s
upload-nightly	0s
	1d 1h 47m 27s

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