Add support for 64-bit architectures in build_aar.py.
Add support for 64-bit architectures in build_aar.py.

BUG=webrtc:7456
NOTRY=True

Review-Url: https://codereview.webrtc.org/2802693005
Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#17587}

ShiftMediaProject/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc,TimothyGu/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc