MicroBuild does not concurrently send files to ESRP on Mac & Linux

[ellahathaway]

Description of the Problem

MicroBuild, the tool responsible for sending files to ESRP for signing, exhibits different behaviors on Windows vs Mac and Linux. On Windows, MicroBuild ships multiple files at a time on multiple threads. On Mac and Linux, MicroBuild send a single file on a single thread to ESRP. This creates timeout issues on Mac & Linux and increases build time significantly. It is the difference between sending one file per thread using a single thread versus sending 50 files per thread using 50 threads.

Current Solution/Status

The MicroBuild team is investigating a fix. Meanwhile, it is possible to increase the thread count for the MicroBuild task. See this section of code (internal Microsoft link)

Although this adjustment won't match the concurrency level of Windows (50 threads each sending one file vs. 50 threads each sending 50 files), it should help reduce build times on Mac and Linux.

[ellahathaway]

Increasing thread count on mac appears to introduce concurrency issues for ESRP. This occurred when the thread count was >= 20. I am investigating if the issue still occurs with a thread count 1 < count < 20

[ellahathaway]

I moved this to be a sub-issue of #4678. The reasoning for this is that this issue preventing me from being able to remove the forced dry-run signing from mac & linux builds in the VMR official pipeline.