Set kernel gcc version to 4.8 for ARM targets

* This causes the check during path setup for an arm-eabi-4.9 toolchain to fail,
      thus only leaving the arm-linux-androideabi- to exist.
* This is only temporary as Google is building with 4.9 and 4.8 gcc's
       have been removed in their next release

Was updated to 4.9 here: https://github.com/CyanogenMod/android_build/commit/bf8346e90c5a6d5d809fa7166d50714b2b6bc30d
Toolchain check here: https://github.com/CyanogenMod/android_build/blob/cm-13.0/envsetup.sh#L189



Change-Id: I24bff10e392a6cdced1797870e523144e83d611d
Signed-off-by: Brandon McAnsh <brandon.mcansh@gmail.com>