Add support for ARM64EC when building with MSVC #924

Job	Run time
Test aarch64-apple-tvos	5m 28s
Test CUDA support	45s
MSRV (ubuntu-latest)	30s
Rustfmt	11s
MSRV (windows-latest)	41s
Test (stable)	42s
Test (beta)	23s
Test (nightly)	29s
Test (linux32)	53s
Test (macos)	33s
Test (aarch64-ios)	46s
Test (win32)	1m 16s
Test (win64)	1m 36s
Test (mingw32)	1m 28s
Test (mingw64)	1m 19s
Test (windows-2019)	1m 32s
Test (windows-aarch64, windows-latest, stable, aarch64-pc-windows-msvc, --no-run)	1m 44s
	20m 16s

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