Use any GCC version
Based on SlimRoms
Google already added this I just added the option to use O3

TARGET_GCC_VERSION := <version-to-use>
eg
TARGET_GCC_VERSION := 4.7

and

TARGET_USE_O3 := <value>
eg
TARGET_USE_O3 := true

Signed-off-by: PipelinerArd <kristoferard@gmail.com>