BES is incompatible with Bazel remote caching on GCS

[amlinux]

I encountered an incompatibility between BES setup in TeamCity and Bazel remote caching on GCS.
Due to a combination of the following facts:

• GCS caching requires passing Google service account credentials to Bazel (--default_google_credentials option).
• Google service account credentials are issued with certain policy restrictions (all connections must be authenticated and encrypted PRIVACY_AND_INTEGRITY) respected by gRPC.
• The same credentials are apllied to all outgoing connections from Bazel (both remote caching and BES are affected).
• BES in the Bazel agent plugin is configured without encryption (protocol grpc:// as opposed to grpcs://).

I see the following errors:

ERROR: The Build Event Protocol upload failed: UNAUTHENTICATED: UNAUTHENTICATED: Credentials require channel with PRIVACY_AND_INTEGRITY security level. Observed security level: NONE

[NikolayPianikov]

@amlinux Alternatively, please use a binary event file for TeamCity integration

[amlinux]

I do use binary event files now. To me it feels like it lacks realtime updates as the build/test progresses. Apparently some buffering is involved there. It would be great to have the proper solution.