Remap Windows targets triples to their LLVM counterparts #1783

Job	Run time
Test build-std (aarch64-tvos)	1m 34s
Test build-std (aarch64-tvos-sim)	1m 38s
Test (stable)	28s
Test build-std (x86_64-tvos)	1m 44s
Test (beta)	57s
Test (nightly)	32s
Rustfmt	12s
Test (linux32)	1m 34s
Test (macos)	2m 39s
Test (aarch64-macos)	42s
Test (aarch64-ios)	1m 7s
Clippy	14s
Test (win32)	1m 36s
Test (win64)	2m 37s
semver-checks	13s
Test (mingw32)	1m 53s
Test (mingw64)	1m 12s
Test wasm (wasm32-unknown-unknown)	26s
Test CUDA support	28s
MSRV (ubuntu-latest)	22s
MSRV (windows-latest)	41s
Test (windows-2019)	3m 12s
MSRV (macos-latest)	26s
Test (windows-aarch64, windows-latest, stable, aarch64-pc-windows-msvc, --no-run)	1m 22s
Test (windows-clang, windows-2019, stable, x86_64-pc-windows-msvc, clang, clang++)	3m 15s
Test (windows-clang-cl, windows-2019, stable, x86_64-pc-windows-msvc, clang-cl, clang-cl)	3m 13s
	34m 17s

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