Apple: Remove redundant flags #1971

Job	Run time
Test wasm (wasm32-unknown-unknown)	20s
Test build-std (aarch64-tvos)	2m 8s
Test CUDA support	26s
Clippy	16s
Rustfmt	4s
Test build-std (aarch64-tvos-sim)	1m 56s
semver-checks	15s
Test build-std (x86_64-tvos)	1m 50s
Test wasm32-wasip1-thread	28s
MSRV (ubuntu-latest)	20s
MSRV (windows-latest)	40s
Test (stable)	49s
MSRV (macos-latest)	32s
Test (beta)	48s
Test (nightly)	48s
Test (linux32)	48s
Test (macos)	50s
Test (aarch64-macos)	34s
Test (aarch64-ios)	46s
Test (win32)	35s
Test (win64)	33s
Test (mingw32)	33s
Test (mingw64)	34s
Test (windows-2019)	36s
Test (windows-aarch64, windows-latest, stable, aarch64-pc-windows-msvc, --no-run)	33s
Test (windows-clang, windows-2019, stable, x86_64-pc-windows-msvc, clang, clang++)	36s
Test (windows-clang-cl, windows-2019, stable, x86_64-pc-windows-msvc, clang-cl, clang-cl)	35s
	19m 13s

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