Switch x86 default compiler to multilib version

Switch from gcc-4.7 32-bit only to gcc-4.7 multilib (32/x32/64) compiler.
Tested x86 image build on Linux and Darwin.

This bionic patch is required:
https://android-review.googlesource.com/#/c/64183

Change-Id: Ifc2c6c5d6a4a1b71a00a87af072bb7f67b1c284d
Signed-off-by: Pavel Chupin <pavel.v.chupin@intel.com>