Enable CI for Loongarch64 #1475

Job	Run time
rust_stable	1m 48s
linux_native_builds (x86_64-unknown-linux-gnu)	2m 8s
linux_native_builds (x86_64-unknown-linux-musl)	2m 1s
macos	2m 38s
macos-aarch64	1m 31s
minver	13s
rustfmt	5s
tier3 (x86_64-unknown-dragonfly)	1m 0s
tier3 (x86_64-unknown-openbsd)	56s
tier3 (x86_64-unknown-haiku)	55s
tier3 (armv7-unknown-linux-uclibceabihf)	1m 3s
tier3 (i686-unknown-hurd-gnu)	54s
cross_compiling	0s
cross	0s
redox	0s
	15m 12s

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