Add support for ARM64EC when building with MSVC #917

Job	Run time
Test aarch64-apple-tvos	2m 49s
MSRV (ubuntu-latest)	29s
Test CUDA support	19s
Rustfmt	5s
MSRV (windows-latest)	51s
Test (stable)	28s
Test (beta)	23s
Test (nightly)	25s
Test (linux32)	39s
Test (macos)	1m 40s
Test (aarch64-ios)	1m 5s
Test (win32)	1m 21s
Test (win64)	2m 18s
Test (mingw32)	1m 26s
Test (mingw64)	1m 27s
Test (windows-2019)	1m 30s
Test (windows-aarch64, windows-latest, stable, aarch64-pc-windows-msvc, --no-run)	1m 12s
	18m 27s

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