relates to:coder/internal#1026

On POSIX systems (macOS and Linux) we compile the dbcleaner binary into a temp directory. This allows us to explicitly separate the compilation step and report the time it takes. We suspect this might be a contributing factor in the above linked flakes we see on macOS.

This doesn't work on Windows because Go tests clean up the temp directory at the end of the test and the dbcleaner binary will still be executing. On Windows you cannot delete a file being executed nor the directory. However, we are not seeing any flakes on Windows so the old behavior seems to be OK.