darkirc: switch recommendation from docker to podman for android builds

bin/darkirc/Makefile

@@ -53,11 +53,12 @@ $(BIN).android64:
 #	cp -f ../../target/armv7-linux-androideabi/release/$(BIN) $(BIN).$@
 
 # This target doesn't require installing any packages from Android Studio
-docker-android:
-	docker build -t test:latest . --file android.Dockerfile
+podman-android:
+	# s/podman/docker/ if you are using docker instead
+	podman build -t test:latest . --file android.Dockerfile
 	# Use this command to get an interactive terminal inside docker:
 	#docker run -v $(shell pwd)/../../:/root/src -it test:latest /bin/bash
-	docker run --rm -v $(shell pwd)/../../:/root/src -t test:latest make _aarch64-android
+	podman run --rm -v $(shell pwd)/../../:/root/src -t test:latest make _aarch64-android
 	cp -f ../../target/aarch64-linux-android/release/darkirc darkirc.aarch64-android
 # Invoked inside docker by the command above
 # We need to mount this directory as a volume using -v so docker can access it

bin/darkirc/android.Dockerfile

@@ -1,4 +1,4 @@
-FROM ubuntu
+FROM docker.io/ubuntu
 ENV DEBIAN_FRONTEND noninteractive
 
 RUN apt-get update

doc/src/misc/darkirc/darkirc.md

@@ -41,12 +41,15 @@ This is for Android 64 bit (which is most phones).
 You will compile darkirc on your computer then copy it to your phone
 and run it in Termux (a command-line terminal for Android).
 
-1. Setup Docker on your computer which may look like:
-    1. Install docker and docker-buildx packages.
-    2. Enable the docker daemon service.
-    3. Add your user to the docker group and refresh the session
-       (either with `su -c $USER` or logout/login).
-2. Run `cd bin/darkirc/ && make docker-android`. The resulting file 
+We will use podman which is a secure replacement for docker. However if you
+prefer to use docker just be aware of
+[the security risks](https://docs.docker.com/engine/security/#docker-daemon-attack-surface).
+Podman is a drop in replacement.
+
+1. Setup podman on your computer which may look like:
+    1. Install podman package
+    2. Enable the podman daemon service.
+2. Run `cd bin/darkirc/ && make podman-android`. The resulting file 
     will be called `darkirc.aarch64-android` (it might be needed to 
     make the file executable `chmod +x darkirc.aarch64-android`). 
     Copy this to your phone.