Too high GOMAXPROCS triggers "module [...] appears multiple times in workspace" error

[geropl]

Bug description

context: https://github.com/gitpod-io/gitpod-next/pull/9019

tl;dr:

• when removing preexisting GOMAXPROCS limitations we ran into a build issue stating go: module github.com/gitpod-io/gitpod-next/backend appears multiple times in workspace
• it seems to be a race (not reproduceable with lower core count/different cache state), and probably in leeway

Steps to reproduce

• take recent main from gitpod-io/gitpod-next
• undo these changes: https://github.com/gitpod-io/gitpod-next/pull/9019
• make a change to backend and push
• see the CI failing with [backend:app] go: module github.com/gitpod-io/gitpod-next/backend appears multiple times in workspace

Expected behavior

No response

Example repository

No response

Anything else?

No response