awk.Makefile: uninstall: also delete empty directories

2 jobs for master in 10 minutes and 50 seconds (queued for 21 minutes and 43 seconds)
Status Job ID Name Coverage
  Test
passed #2366
coq
iris-coq8.5.3

00:05:58

passed #2367
coq
iris-coq8.6

00:04:51