Disable protobuf deterministic randomness in soong_build

Soong writes out text protos for the sbox manifests, and if those change
every time soong changes, we trigger rebuilds of significant portions of
the tree. This is very annoying when attempting to iterate on Soong, so
disable this functionality at the soong_build level.

Bug: 200727888
Change-Id: Icf21e1775a4c4200e983c1b8ac66ddd780d7c90c