kerneltoolchains: Add option to force usage of GCC 4.7/4.8
kerneltoolchains: Add option to force usage of GCC 4.7/4.8

'''
 Before 'options' are:
 - Android '4.9', Android '4.8', Android '4.7'
 Now options are:
 - Android '4.9', Android '4.8', GCC 'gcc-4.8', Android '4.7', GCC 'gcc-4.7'
'''
* Old kernels not are compatible with Android 4.7, and if we merge
  "ARM: msm: GCC Version change."@I7b5c9212e63826a0cb5b7e4ab161737ae87a2157
  it makes GCC 4.7 incompatible and Android KitKat not buildable

Change-Id: Ic65da091ccfe3c55c42d725a42d91e44490b3a9c
Signed-off-by: Caio Oliveira <4db4e54f91055ffa8197b8408ec5b5470f9993b8@gmail.com>

AdrianDC/android_development_shell_tools,AdrianDC/android_development_shell_tools