Build

Add CMake toolchains #96

Job	Run time
Native build	24s
Cross build (alpha-unknown-linux-gnu)	5m 1s
Cross build (x86_64-unknown-linux-gnu)	9m 46s
Cross build (i386-unknown-linux-gnu)	10m 8s
Cross build (arm-unknown-linux-gnueabi)	5m 17s
Cross build (arm-unknown-linux-gnueabihf)	5m 28s
Cross build (hppa-unknown-linux-gnu)	4m 56s
Cross build (aarch64-unknown-linux-gnu)	5m 19s
Cross build (mips-unknown-linux-gnu)	5m 11s
Cross build (mipsel-unknown-linux-gnu)	5m 12s
Cross build (powerpc-unknown-linux-gnu)	5m 31s
Cross build (s390-unknown-linux-gnu)	5m 21s
Cross build (s390x-unknown-linux-gnu)	5m 21s
Cross build (sparc-unknown-linux-gnu)	5m 31s
Cross build (powerpc64le-unknown-linux-gnu)	5m 32s
	1h 23m 58s

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