Don't inherit the `/Oy` flag for 64-bit targets #2132

Job	Run time
Test wasm (wasm32-unknown-unknown)	13s
Test build-std (aarch64-tvos)	1m 52s
Test CUDA support	43s
Test build-std (aarch64-tvos-sim)	1m 58s
Clippy	5s
MSRV (ubuntu-latest)	19s
Test build-std (x86_64-tvos)	1m 56s
MSRV (windows-latest)	39s
Rustfmt	11s
semver-checks	2m 32s
MSRV (macos-latest)	26s
Test (stable)	1m 57s
Test wasm32-wasip1-thread	32s
Test (beta)	1m 40s
Test (nightly)	2m 1s
Test (linux32)	2m 9s
Test (macos)	3m 55s
Test (aarch64-macos)	1m 34s
Test (aarch64-ios)	1m 34s
Test (win32)	2m 55s
Test (win64)	3m 29s
Test (mingw32)	2m 47s
Test (mingw64)	3m 13s
Test (windows-2019)	3m 9s
Test (windows-aarch64, windows-latest, stable, aarch64-pc-windows-msvc, --no-run)	4m 4s
Test (windows-clang, windows-2019, stable, x86_64-pc-windows-msvc, clang, clang++)	3m 39s
Test (windows-clang-cl, windows-2019, stable, x86_64-pc-windows-msvc, clang-cl, clang-cl)	3m 37s
	53m 9s

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