adjust ROM/Kernel GCC readout

(cherry picked from commit 711675b64d78518ef69d4694be93c2d8357d14e1)

Conflicts:
	core/dumpvar.mk
Let the variables do their jobs

We dont want to hard code the flags here as it will override device BoardConfig.

This will build ROM 4.8 and Kernel 4.7 as default and still allow you to change them if you want. To build with other toolchains add these flags to your BoardConfig

TARGET_GCC_VERSION_AND := (ROM Toolchain to use)
TARGET_GCC_VERSION_ARM := (Kernel toolchain to use)

If a flag is not set, it will go back to the default value

(cherry picked from commit d52cbc8bd21288f146d631eab8c53ad5ea08d5ae)

Conflicts:
	core/combo/TARGET_linux-arm.mk