extract_kernel.py: add support to output compiler information

Test: tested with android-mainline gki kernel from
    https://android.googlesource.com/kernel/prebuilts/mainline/arm64/



Signed-off-by: Yongqin Liu <yongqin.liu@linaro.org>
Change-Id: Ibf3eeb3679b233cd0d54501d385f442e0c0c34ec