sys: add MIPS R6 support #41

Job	Run time
minver	11s
macos	1m 23s
rust_stable	54s
rustfmt	10s
tier3 (x86_64-unknown-dragonfly)	50s
tier3 (x86_64-unknown-openbsd)	57s
tier3 (armv7-unknown-linux-uclibceabihf)	1m 0s
linux_native_builds (x86_64-unknown-linux-gnu)	1m 3s
tier3 (x86_64-unknown-haiku)	1m 21s
linux_native_builds (x86_64-unknown-linux-musl)	1m 1s
redox	44s
cross (arm-unknown-linux-gnueabi)	1m 31s
cross_compiling (aarch64-linux-android)	50s
cross (armv7-unknown-linux-gnueabihf)	2m 54s
cross_compiling (arm-linux-androideabi)	47s
cross (i686-unknown-linux-gnu)	2m 13s
cross_compiling (armv7-linux-androideabi)	54s
cross (i686-unknown-linux-musl)	2m 37s
cross_compiling (i686-linux-android)	42s
cross (mips-unknown-linux-gnu)	1m 33s
cross_compiling (x86_64-linux-android)	33s
cross (mips64-unknown-linux-gnuabi64)	1m 34s
cross_compiling (arm-unknown-linux-musleabi)	38s
cross (mips64el-unknown-linux-gnuabi64)	1m 36s
cross_compiling (x86_64-unknown-fuchsia)	26s
cross (mipsel-unknown-linux-gnu)	1m 30s
cross_compiling (x86_64-unknown-illumos)	45s
cross (powerpc64le-unknown-linux-gnu)	1m 34s
cross_compiling (aarch64-apple-ios, true)	26s
cross_compiling (powerpc64-unknown-linux-gnu)	51s
cross_compiling (s390x-unknown-linux-gnu)	36s
cross_compiling (x86_64-unknown-linux-gnux32)	32s
cross_compiling (x86_64-unknown-netbsd)	28s
	35m 4s

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