Fix Apple clang determination bug. #6629

Job	Run time
ubuntu-latest-cmake	1m 25s
ubuntu-focal-make	1m 20s
macOS-latest-make	3m 6s
macOS-latest-cmake	3m 13s
ubuntu-latest-cmake-mpi (mpich)	1m 31s
ubuntu-latest-cmake-sanitizer (ADDRESS, Debug)	3m 47s
ubuntu-latest-cmake-mpi (libopenmpi-dev)	1m 35s
ubuntu-latest-cmake-sanitizer (ADDRESS, Release)	3m 30s
ubuntu-latest-cmake-sanitizer (THREAD, Debug)	7m 59s
ios-xcode-build	1m 1s
macOS-latest-cmake-tvos	2m 20s
macOS-latest-cmake-ios	1m 37s
ubuntu-latest-cmake-sanitizer (THREAD, Release)	4m 49s
ubuntu-latest-cmake-sanitizer (UNDEFINED, Debug)	3m 16s
macOS-latest-swift (generic/platform=macOS)	3m 17s
windows-latest-cmake (noavx, -DLLAMA_NATIVE=OFF -DLLAMA_BUILD_SERVER=ON -DLLAMA_AVX=OFF -DLLAMA_A...	2m 46s
ubuntu-latest-cmake-sanitizer (UNDEFINED, Release)	3m 29s
windows-latest-cmake-cublas (12.2.0, cublas)	16m 9s
macOS-latest-swift (generic/platform=iOS)	2m 36s
windows-latest-cmake (avx2, -DLLAMA_NATIVE=OFF -DLLAMA_BUILD_SERVER=ON -DBUILD_SHARED_LIBS=ON)	2m 41s
windows-latest-cmake-cublas (11.7.1, cublas)	17m 35s
macOS-latest-swift (generic/platform=tvOS)	2m 23s
windows-latest-cmake (avx, -DLLAMA_NATIVE=OFF -DLLAMA_BUILD_SERVER=ON -DLLAMA_AVX2=OFF -DBUILD_SH...	2m 48s
windows-latest-cmake (avx512, -DLLAMA_NATIVE=OFF -DLLAMA_BUILD_SERVER=ON -DLLAMA_AVX512=ON -DBUIL...	4m 45s
windows-latest-cmake (clblast, -DLLAMA_NATIVE=OFF -DLLAMA_BUILD_SERVER=ON -DLLAMA_CLBLAST=ON -DBU...	2m 7s
windows-latest-cmake (openblas, -DLLAMA_NATIVE=OFF -DLLAMA_BUILD_SERVER=ON -DLLAMA_BLAS=ON -DBUIL...	2m 2s
release	0s
	1h 43m 7s

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