Ensure dist-dir test has fresh start (#19370)
Ensure dist-dir test has fresh start (#19370)

h/t to @prateekbh for noticing this test isn't cleaning up properly 

Closes: https://github.com/vercel/next.js/issues/19369
azukaru/next.js,JeromeFitz/next.js,zeit/next.js,zeit/next.js,JeromeFitz/next.js,azukaru/next.js,flybayer/next.js,flybayer/next.js,JeromeFitz/next.js,flybayer/next.js,flybayer/next.js,zeit/next.js,azukaru/next.js,azukaru/next.js,JeromeFitz/next.js