Stale errors/warnings stick around after a full build

[natefaubion]

On 0.26.3, my usual steps to reproduce involve git checkout workflows:

• Open a git project in VSCode
• Save a file in the editor that results in an error or warning
• git checkout .
• Initiate a full build in the editor with cmd+shift+b
• Project builds OK but errors and warnings stick around.

In order to get rid of the error I have to go to the file and resave it. In the case of a file that no longer exists, I have to reload the workspace in VScode.