docker: refactor and update docker image build

Fixes tailscale/tailscale#15674

update docker image datestamp
make docker-shell target use the build image with an explicit /bin/bash command
retain the docker-remove-shell-image target in case something depends on it, but clarify that it is now a no-op
hoist all ENV declarations
hoist all mkdir commands
combine mkdir commands
use env vars in mkdir
combine apt-get commands into single RUN
make argument order consistent in apt-get commands
collect packages into fewer apt-get commands
add clean up of temporary files after apt-get
expand apt-get commands to one package per line
sort packages in apt-get commands
combine go installation commands into single RUN
update golang version to 1.24.1
also copy build.gradle file
ensure gradlew is executable before running
remove trailing newline

per review comment, extract multiline apt-get command
into shell script, copy and run that shell script within
image during docker build

Signed-off-by: Sam Mikes (He/him/his) <[email protected]>

Author: Sam Mikes (He/him/his)

Makefile

@@ -10,7 +10,7 @@
 # with this name, it will be used.
 #
 # The convention here is tailscale-android-build-amd64-<date>
-DOCKER_IMAGE := tailscale-android-build-amd64-031325-1
+DOCKER_IMAGE := tailscale-android-build-amd64-041425-1
 export TS_USE_TOOLCHAIN=1
 
 # Auto-select an NDK from ANDROID_HOME (choose highest version available)
@@ -355,13 +355,12 @@ docker-remove-build-image: ## Removes the current docker build image
 docker-all: docker-build-image docker-run-build $(DOCKER_IMAGE)
 
 .PHONY: docker-shell
-docker-shell: ## Builds a docker image with the android build env and opens a shell
-	docker build -f docker/DockerFile.amd64-shell -t tailscale-android-shell-amd64 .
-	docker run --rm -v $(CURDIR):/build/tailscale-android -it tailscale-android-shell-amd64
+docker-shell: docker-build-image ## Builds a docker image with the android build env and opens a shell
+	docker run --rm -v $(CURDIR):/build/tailscale-android -it $(DOCKER_IMAGE) /bin/bash
 
 .PHONY: docker-remove-shell-image
 docker-remove-shell-image: ## Removes all docker shell image
-	docker rmi --force tailscale-android-shell-amd64
+	@echo "docker-remove-shell-image retained for backward compatibility, but is a no-op; docker-shell now uses build image"
 
 .PHONY: clean
 clean: ## Remove build artifacts. Does not purge docker build envs. Use dockerRemoveEnv for that.

docker/DockerFile.amd64-build

@@ -3,31 +3,30 @@
 
 FROM --platform=linux/amd64 eclipse-temurin:21
 
-# To enable running android tools such as aapt
-RUN apt-get update && apt-get -y upgrade
-RUN apt-get install -y libz1 libstdc++6 unzip zip
-# For Go:
-RUN apt-get -y --no-install-recommends install curl gcc
-RUN apt-get -y --no-install-recommends install ca-certificates libc6-dev git
-
-RUN apt-get -y install make
-
-RUN mkdir -p build
 ENV HOME /build
-
-# Make android sdk location, the later make step will populate it.
-RUN mkdir android-sdk
 ENV ANDROID_HOME $HOME/android-sdk
 ENV ANDROID_SDK_ROOT $ANDROID_HOME
 ENV PATH $PATH:$HOME/bin:$ANDROID_HOME/platform-tools
 
+RUN mkdir -p \
+    ${HOME} \
+    /android-sdk \
+    ${ANDROID_HOME} \
+    $HOME/tailscale-android
+
+# To enable running android tools such as aapt
+COPY scripts/docker-build-apt-get.sh /tmp
+RUN chmod 755 /tmp/docker-build-apt-get.sh && \
+    /tmp/docker-build-apt-get.sh && \
+    rm -f /tmp/docker-build-apt-get.sh
+
 # We need some version of Go new enough to support the "embed" package
 # to run "go run tailscale.com/cmd/printdep" to figure out which Tailscale Go
 # version we need later, but otherwise this toolchain isn't used:
-RUN curl -L https://go.dev/dl/go1.23.0.linux-amd64.tar.gz | tar -C /usr/local -zxv
-RUN ln -s /usr/local/go/bin/go /usr/bin
+RUN \
+    curl -L https://go.dev/dl/go1.24.1.linux-amd64.tar.gz | tar -C /usr/local -zxv && \
+    ln -s /usr/local/go/bin/go /usr/bin
 
-RUN mkdir -p $HOME/tailscale-android
 RUN git config --global --add safe.directory $HOME/tailscale-android
 WORKDIR $HOME/tailscale-android
 
@@ -37,10 +36,11 @@ COPY Makefile Makefile
 RUN make androidsdk
 
 # Preload Gradle
-COPY android/gradlew android/gradlew
+COPY android/gradlew android/build.gradle android
 COPY android/gradle android/gradle
-RUN ./android/gradlew
+
+RUN chmod 755 android/gradlew && \
+    ./android/gradlew
 
 # Build the android app, bump the playstore version code, and make the tv release
 CMD make clean && make release && make bump_version_code && make release-tv
-

docker/DockerFile.amd64-shell

@@ -0,0 +1,39 @@
+#!/bin/sh
+#
+# Copyright (c) Tailscale Inc & AUTHORS
+# SPDX-License-Identifier: BSD-3-Clause
+#
+# docker-build-apt-get.sh runs 'apt'-related commands inside
+# the environment that /builds the docker image/
+set -x
+set -e
+
+apt-get update
+apt-get -y upgrade
+
+apt-get -y install \
+        \
+	libstdc++6 \
+	libz1 \
+	make \
+	unzip \
+	zip \
+	\
+	# end of sort region
+
+apt-get -y --no-install-recommends install \
+    \
+    ca-certificates \
+    curl \
+    gcc \
+    git \
+    libc6-dev \
+    \
+    # end of sort region
+
+apt-get -y clean
+
+rm -rf \
+   /var/cache/debconf \
+   /var/lib/apt/lists \
+   /var/lib/apt/dpkg