PacProccesor: Only build for 32-bit

PacProcessor relies on libpac from chromium, which is not built
for 64b right now.

(cherry picked from commit f8749200c06a8714ffd46f5e2ec81be57ad4f7f4)

Change-Id: Ic128e17b7437c130df29eeab3293b9c01f01d70b
Merge "PacProccesor: Only build for 32-bit"