Revert "Use gcc 4.9.x for x86_64-linux"

This reverts commit ea828056bc06705d369aedf2905e6cadaaa9fd93.
Revert "GCC: use SM host toolchains"

This reverts commit 46357a7c9d0707724b19cbc9b1690ef753b5f75a.
Use sabermod host toolchains

Change-Id: I413fb86a61d787e4f7d7dbea78c02b13be813759

Use gcc 4.9.x for x86_64-linux
use x86_64-linux-4.9 for 32bit code

sabermod toolchains have m32 and x32 code built-in.