Add CMake toolchains #98

Job	Run time
Native build	18s
Cross build (alpha-unknown-linux-gnu)	5m 46s
Cross build (x86_64-unknown-linux-gnu)	21m 43s
Cross build (i386-unknown-linux-gnu)	21m 46s
Cross build (arm-unknown-linux-gnueabi)	9m 10s
Cross build (arm-unknown-linux-gnueabihf)	14m 37s
Cross build (hppa-unknown-linux-gnu)	5m 41s
Cross build (aarch64-unknown-linux-gnu)	15m 6s
Cross build (mips-unknown-linux-gnu)	9m 33s
Cross build (mipsel-unknown-linux-gnu)	8m 57s
Cross build (powerpc-unknown-linux-gnu)	19m 20s
Cross build (s390-unknown-linux-gnu)	6m 41s
Cross build (s390x-unknown-linux-gnu)	19m 7s
Cross build (sparc-unknown-linux-gnu)	17m 46s
Cross build (powerpc64le-unknown-linux-gnu)	19m 31s
	3h 15m 2s

Provide feedback