NPM builds don't support cross compiling and will always compile for the host.
Binding.gyp now uses mraa_NPM_SRCS instead of mraa_LIB_SRCS_NOAUTO which
contains all platforms. Cmake now uses mraa_LIB_PLAT_SRCS_NOAUTO to provide all
the sources. NPM builds will build objects for all platforms reguardless of
space which does meann slightly bigger binaries.
Signed-off-by: Brendan Le Foll <brendan.le.foll@intel.com>
