Revert "build: clean up s6 overlay structure"

This reverts commit 90420823b0.

root/etc/s6-overlay/s6-rc.d/svc-nginx/run

@@ -1,3 +1,16 @@
 #!/usr/bin/with-contenv bash
 # shellcheck shell=bash
+
+if pgrep -f "[n]ginx:" >/dev/null; then
+    echo "Zombie nginx processes detected, sending SIGTERM"
+    pkill -ef [n]ginx:
+    sleep 1
+fi
+
+if pgrep -f "[n]ginx:" >/dev/null; then
+    echo "Zombie nginx processes still active, sending SIGKILL"
+    pkill -9 -ef [n]ginx:
+    sleep 1
+fi
+
 # exec /usr/sbin/nginx