allow users to explicitly specify device id #159

Job	Run time
mix_compile (i686-linux-gnu, cc_toolchain/i686-linux-gnu.cmake, gcc-i686-linux-gnu, g++-i686-linu...	35m 57s
mix_compile (aarch64-linux-gnu, cc_toolchain/aarch64-linux-gnu.cmake, gcc-aarch64-linux-gnu, g++-...	37m 53s
mix_compile (armv7l-linux-gnueabihf, cc_toolchain/armv7l-linux-gnueabihf.cmake, gcc-arm-linux-gnu...	32m 50s
mix_compile (armv6-linux-gnueabihf, cc_toolchain/armv6-nerves-linux-gnueabihf.cmake, armv6-nerves...	34m 21s
mix_compile (ppc64le-linux-gnu, cc_toolchain/ppc64le-linux-gnu.cmake, gcc-powerpc64le-linux-gnu, ...	33m 42s
mix_compile (s390x-linux-gnu, cc_toolchain/s390x-linux-gnu.cmake, gcc-s390x-linux-gnu, g++-s390x-...	31m 53s
mix_compile (riscv64-linux-gnu, cc_toolchain/riscv64-linux-gnu.cmake, gcc-riscv64-linux-gnu, g++-...	1h 0m 37s
	4h 27m 13s

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