Added a simple README.md. #10

Job	Run time
Build (qemu_x86_defconfig, glibc)	52m 2s
Build (qemu_x86_defconfig, uclibc)	46m 20s
Build (qemu_x86_defconfig, musl)	48m 4s
Build (qemu_x86_64_defconfig, glibc)	50m 32s
Build (qemu_x86_64_defconfig, uclibc)	48m 57s
Build (qemu_x86_64_defconfig, musl)	46m 9s
Build (raspberrypi4_defconfig, glibc)	1h 10m 18s
Build (raspberrypi4_defconfig, uclibc)	1h 3m 31s
Build (raspberrypi4_defconfig, musl)	1h 2m 32s
Build (raspberrypi4_64_defconfig, glibc)	1h 10m 35s
Build (raspberrypi4_64_defconfig, uclibc)	1h 6m 44s
Build (raspberrypi4_64_defconfig, musl)	1h 4m 37s
Build (qemu_ppc64le_pseries_defconfig, glibc)	59m 52s
Build (qemu_ppc64le_pseries_defconfig, uclibc)	58m 28s
Build (qemu_ppc64le_pseries_defconfig, musl)	51m 36s
Build (qemu_mips32r2_malta_defconfig, glibc)	48m 34s
Build (qemu_mips32r2_malta_defconfig, uclibc)	46m 8s
Build (qemu_mips32r2_malta_defconfig, musl)	44m 34s
Build (qemu_mips64_malta_defconfig, glibc)	51m 17s
Build (qemu_mips64_malta_defconfig, uclibc)	47m 5s
Build (qemu_mips64_malta_defconfig, musl)	46m 18s
	19h 4m 13s

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