Docker build env for windows/android

docker/build-env/android/Dockerfile

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+# Android build environment.
+#
+# Mirrors the toolchain pinned by .github/workflows/mobile-build-validation.yml
+# so a `gomobile bind` against ./client/android in this image produces the
+# same netbird.aar that CI builds.
+#
+# Tooling versions (must stay in sync with the CI workflow):
+#   - Ubuntu 22.04 (matches the ubuntu-latest GitHub runner)
+#   - Go 1.25.5 (matches go.mod)
+#   - Adopt JDK 11 (matches actions/setup-java@v3 java-version: 11, distribution: adopt)
+#   - Android SDK cmdline-tools 8512546
+#   - Android NDK 23.1.7779620
+#   - gomobile commit v0.0.0-20251113184115-a159579294ab
+#
+# Usage (from the netbird repo root):
+#
+#   docker build -t netbird/build-android docker/build-env/android
+#
+#   # bind the netbird checkout in and run the same gomobile command CI runs
+#   docker run --rm -v "$PWD:/src" -w /src netbird/build-android \
+#       gomobile bind \
+#       -o netbird.aar \
+#       -javapkg=io.netbird.gomobile \
+#       -ldflags="-checklinkname=0 \
+#                 -X golang.zx2c4.com/wireguard/ipc.socketDirectory=/data/data/io.netbird.client/cache/wireguard \
+#                 -X github.com/netbirdio/netbird/version.version=local" \
+#       ./client/android
+#
+# To build the full APK, mount the android-client repo too and run
+# `./gradlew assembleDebug` from /android-client (this image carries
+# gradle's prerequisites JDK + Android SDK but not the gradle wrapper —
+# that ships with android-client).
+
+FROM ubuntu:22.04
+
+ARG DEBIAN_FRONTEND=noninteractive
+
+# Versions — bump in lockstep with .github/workflows/mobile-build-validation.yml.
+ARG GO_VERSION=1.25.5
+ARG ANDROID_CMDLINE_TOOLS_VERSION=8512546
+ARG ANDROID_NDK_VERSION=23.1.7779620
+ARG GOMOBILE_VERSION=v0.0.0-20251113184115-a159579294ab
+
+ENV ANDROID_HOME=/opt/android-sdk
+ENV ANDROID_NDK_HOME=${ANDROID_HOME}/ndk/${ANDROID_NDK_VERSION}
+ENV JAVA_HOME=/usr/lib/jvm/java-11-openjdk-amd64
+ENV GOPATH=/go
+ENV GOTOOLCHAIN=local
+ENV CGO_ENABLED=0
+ENV PATH=${GOPATH}/bin:/usr/local/go/bin:${ANDROID_HOME}/cmdline-tools/latest/bin:${ANDROID_HOME}/platform-tools:${JAVA_HOME}/bin:${PATH}
+
+RUN apt-get update && apt-get install -y --no-install-recommends \
+        ca-certificates \
+        curl \
+        unzip \
+        git \
+        openjdk-11-jdk-headless \
+        build-essential \
+    && rm -rf /var/lib/apt/lists/*
+
+# Install Go (matches go.mod). actions/setup-go fetches the same tarball.
+RUN curl -fsSL "https://go.dev/dl/go${GO_VERSION}.linux-amd64.tar.gz" \
+        | tar -C /usr/local -xz \
+    && go version
+
+# Install Android SDK command-line tools, accept licenses, install NDK.
+RUN mkdir -p "${ANDROID_HOME}/cmdline-tools" \
+    && curl -fsSL -o /tmp/cmdline.zip \
+        "https://dl.google.com/android/repository/commandlinetools-linux-${ANDROID_CMDLINE_TOOLS_VERSION}_latest.zip" \
+    && unzip -q /tmp/cmdline.zip -d "${ANDROID_HOME}/cmdline-tools" \
+    && mv "${ANDROID_HOME}/cmdline-tools/cmdline-tools" "${ANDROID_HOME}/cmdline-tools/latest" \
+    && rm /tmp/cmdline.zip \
+    && yes | sdkmanager --licenses > /dev/null \
+    && sdkmanager --install "ndk;${ANDROID_NDK_VERSION}" "platform-tools" > /dev/null
+
+# Install gomobile at the same commit CI pins. Don't run `gomobile init` here:
+# `init` resolves the NDK at runtime, do it on the first bind in the mounted
+# workspace so the cache lands on the host volume.
+RUN GOBIN=/usr/local/bin go install "golang.org/x/mobile/cmd/gomobile@${GOMOBILE_VERSION}" \
+    && gomobile version
+
+WORKDIR /src
+
+# Default entrypoint is a plain shell so the image is composable: callers pass
+# the full gomobile / gradle command they want to run.
+CMD ["/bin/bash"]