Makefile: Error on TOOLCHAIN=gcc-4.9 GCC 4.9 has been removed from the AOSP repo. We marked it deprecated a while back but now it really doesn't work. Bug: 193407077 Test: TOOLCHAIN=gcc-4.9 make linux_image Change-Id: I2fe9838b4f87919867adc5c61084ce68c0af7962