Add CMake toolchains #105

Job	Run time
Native build	16s
Cross build (alpha-unknown-linux-gnu)	3m 26s
Cross build (x86_64-unknown-linux-gnu)	27m 20s
Cross build (i386-unknown-linux-gnu)	27m 20s
Cross build (arm-unknown-linux-gnueabi)	5m 52s
Cross build (arm-unknown-linux-gnueabihf)	8m 12s
Cross build (hppa-unknown-linux-gnu)	3m 20s
Cross build (aarch64-unknown-linux-gnu)	8m 32s
Cross build (mips-unknown-linux-gnu)	4m 38s
Cross build (mipsel-unknown-linux-gnu)	4m 42s
Cross build (powerpc-unknown-linux-gnu)	7m 36s
Cross build (s390-unknown-linux-gnu)	3m 54s
Cross build (s390x-unknown-linux-gnu)	8m 7s
Cross build (sparc-unknown-linux-gnu)	7m 33s
Cross build (powerpc64le-unknown-linux-gnu)	7m 49s
	2h 8m 37s

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