Pull in X86 targets for GVR prebuilts CL@144004555

Also updates the build_gvr_prebuilts.sh script for future prebuilt pull in.

Bug: 34787305
Test: m -j PRODUCT-sdk_google_phone_x86_64-sdk_addon
Test: m -j PRODUCT-sdk_google_phone_mips-sdk_addon

Change-Id: Iba4c4edbdb97f8c2e0e3e6bf054366c2648884fd