Dockerfile: build as non-root user

Dockerfile

@@ -12,16 +12,24 @@ file \
 build-essential \
 && rm -rf /var/lib/apt/lists/*
 
-ENV ANDROID_SDK_ROOT /android-sdk
+ARG USER=deltachat
+ARG UID=1000
+ARG GID=1000
 
-WORKDIR /android-sdk
+RUN groupadd -g $GID -o $USER
+RUN useradd -m -u $UID -g $GID -o $USER
+USER $USER
+
+ENV ANDROID_SDK_ROOT /home/${USER}/android-sdk
+RUN mkdir ${ANDROID_SDK_ROOT}
+WORKDIR $ANDROID_SDK_ROOT
 RUN wget -q https://dl.google.com/android/repository/commandlinetools-linux-6200805_latest.zip && \
   unzip commandlinetools-linux-6200805_latest.zip && \
   rm commandlinetools-linux-6200805_latest.zip
 
 RUN yes | ${ANDROID_SDK_ROOT}/tools/bin/sdkmanager --sdk_root=${ANDROID_SDK_ROOT} --licenses
 
-ENV PATH ${PATH}:/android-sdk/tools/bin
+ENV PATH ${PATH}:${ANDROID_SDK_ROOT}/tools/bin
 
 # Install NDK manually. Other SDK parts are installed automatically by gradle.
 RUN sdkmanager --sdk_root=${ANDROID_SDK_ROOT} ndk-bundle
@@ -30,4 +38,4 @@ ENV ANDROID_NDK_ROOT ${ANDROID_SDK_ROOT}/ndk-bundle
 ENV PATH ${PATH}:${ANDROID_NDK_ROOT}/toolchains/llvm/prebuilt/linux-x86_64/bin/:${ANDROID_NDK_ROOT}
 
 RUN curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y --default-toolchain none
-ENV PATH ${PATH}:/root/.cargo/bin
+ENV PATH ${PATH}:/home/${USER}/.cargo/bin