Common cross compiler configuration

[jw3]

This is being copied around in every client project and should be moved up to commons

if (NOT CROSS_COMPILER_PREFIX)
    set(CROSS_COMPILER_PREFIX "/usr/local/gcc-arm")
endif ()

set(CMAKE_TRY_COMPILE_TARGET_TYPE STATIC_LIBRARY)

set(CMAKE_C_COMPILER "${CROSS_COMPILER_PREFIX}/bin/arm-none-eabi-gcc")
set(CMAKE_CXX_COMPILER "${CROSS_COMPILER_PREFIX}/bin/arm-none-eabi-g++")
set(CMAKE_ASM_COMPILER "${CROSS_COMPILER_PREFIX}/bin/arm-none-eabi-as")
set(CMAKE_AR "${CROSS_COMPILER_PREFIX}/bin/arm-none-eabi-ar" CACHE FILEPATH "Archiver")
set(CMAKE_RANLIB "${CROSS_COMPILER_PREFIX}/bin/arm-none-eabi-ranlib")