pkg/analyzer/test/src/context/builder_test broken on Windows

[sortie]

The following tests are now failing:

BOT	TEST	RESULT	EXPECTED
analyzer-win-release/unittest-asserts	pkg/analyzer/test/src/context/builder_test	RuntimeError	Pass
pkg-win-release	pkg/analyzer/test/src/context/builder_test	RuntimeError	Pass

This seems to have happened between fafd3d0 and 3e5e05d (6 commits), however there was a CI outage and it's not clear which commit introduced the failure. I would guess b58aa3b "Add PubWorkspace, integrate it into ContextBuilder, and therefore fix sealed test" by @srawlins since it's the only commit to change something called context and builder.

If these regressions are intentional, they should be approved per the new status file free workflow to turn the builders green.