[ARM] Extend the usage of TARGET_GCC_VERSION for gdb and arm-eabi-*.

In the future to upgrade the gcc version we just need to edit one
line in core/config.mk.

Change-Id: I01bb38c38f2388913bb7369aa4b2da480411dfbe
Export TARGET_GCC_VERSION as an env variable.

Have it referenced by the adbs tool to pick the specified toolchain.

Change-Id: I23df88946254a55d0749d6753e54559faf33e121
Use GCC 4.7 from google

Thanks aaronpoweruser for saving me hours of fixing errors myself.

Change-Id: I85cdd49a802bc9577e40bccbcfa2b08f3c76a472
Signed-off-by: Stevespear426 <stephen.k.spear@gmail.com>

Conflicts:
	core/config.mk
Add TARGET_GCC_VERSION
toolchain support changes