Map riscv64 linux to linux64-riscv64 and setup CI #444

Job	Run time
Rustfmt	12s
Test (x86_64-unknown-linux-gnu, stable, ubuntu-latest)	4m 55s
Test (x86_64-unknown-linux-gnu, beta, ubuntu-latest)	4m 57s
Test (x86_64-unknown-linux-gnu, nightly, ubuntu-latest)	4m 57s
Test (x86_64-apple-darwin, stable, macos-latest)	6m 58s
Test (aarch64-apple-darwin, nightly, macos-latest)	4m 43s
Test (i686-unknown-linux-gnu, stable, ubuntu-latest)	2m 52s
Test (arm-unknown-linux-gnueabi, stable, ubuntu-latest)	3m 1s
Test (aarch64-unknown-linux-gnu, stable, ubuntu-latest)	3m 3s
Test (riscv64gc-unknown-linux-gnu, stable, ubuntu-latest)	2m 51s
Test (x86_64-unknown-linux-musl, stable, ubuntu-latest)	2m 37s
Test (x86_64-pc-windows-gnu, stable, ubuntu-latest)	5m 4s
Test (i686-pc-windows-msvc, stable-i686-msvc, windows-2019)	19m 11s
Test (i686-pc-windows-msvc, stable-i686-msvc, windows-2019, yes)	19m 30s
Test (x86_64-pc-windows-msvc, stable-x86_64-msvc, windows-latest)	20m 15s
Test (x86_64-pc-windows-msvc, stable-x86_64-msvc, windows-latest, yes)	19m 47s
Test (x86_64-pc-windows-msvc, stable-x86_64-msvc, windows-latest, installed)	20m 34s
	2h 25m 27s

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