Revert "Switch x86 and x86_64 build to use GCC 4.9"

This reverts commit 533c7aa6a293659541222f0dd89bee044ba71a2a.

(cherry picked from commit f123057f5e080687ce17e0e9c23a62954db53f39)

Change-Id: I6dd4ccb100341cf6ebf83829448b0ca7395d5468
2 files changed