fix: Remove /usr/etc in cleanup since it's not used by bootc

Author: gmpinder

scripts/post_build.sh

@@ -2,7 +2,7 @@
 
 set -euo pipefail
 
-rm -rf /tmp/* /var/*
+rm -rf /tmp/* /var/* /usr/etc
 
 if command -v bootc > /dev/null; then
   bootc container lint