A previous build failure with the same inputs but different processor implementation will still fail

[ZacSweers]

Given this scenario

1. Build project consuming a KSP
2. Project fails to compile due to bug in generated code
3. Change KSP impl to fix it
4. Recompile project
5. Project still fails with previous error message, even though generated code is now correct. Requires cleaning first

[ting-yuan]

Should be fixed as a side-effect of #130.

[ting-yuan]

Should be fixed as a side-effect of #130.