Use non-root user when using docker

We now use a non-root user when building packages using a docker
container. This allows detecting misconfigured packages which try
to install files outside of $TERMUX_PREFIX or otherwise mess with
the system during a build.

scripts/Dockerfile

@@ -9,26 +9,28 @@ FROM ubuntu:16.10
 # Fix locale to avoid warnings:
 ENV LANG C.UTF-8
 
-# We expect this to be mounted with '-v $PWD:/root/termux-packages':
-WORKDIR /root/termux-packages
-
 # Needed for setup:
 ADD ./setup-ubuntu.sh /tmp/setup-ubuntu.sh
 ADD ./setup-android-sdk.sh /tmp/setup-android-sdk.sh
 
-# Allow configure to be run as root:
-ENV FORCE_UNSAFE_CONFIGURE 1
-
 # Setup needed packages and the Android SDK and NDK:
 RUN apt-get update && \
-    DEBIAN_FRONTEND=noninteractive apt-get install -yq sudo && \
-    /tmp/setup-ubuntu.sh && \
-    apt-get clean && \
-    /tmp/setup-android-sdk.sh && \
+    apt-get -yq upgrade && \
+    apt-get install -yq sudo && \
+    adduser --disabled-password --shell /bin/bash --gecos "" builder && \
+    echo "builder ALL=(root) NOPASSWD:ALL" > /etc/sudoers.d/builder && \
+    chmod 0440 /etc/sudoers.d/builder && \
+    su - builder -c /tmp/setup-ubuntu.sh && \
+    su - builder -c /tmp/setup-android-sdk.sh && \
     # Removed unused parts to make a smaller Docker image:
-    cd /root/lib/android-ndk/ && \
+    apt-get clean && \
+    rm -rf /var/lib/apt/lists/* && \
+    cd /home/builder/lib/android-ndk/ && \
     rm -Rf toolchains/mips* && \
     rm -Rf sources/cxx-stl/gabi++ sources/cxx-stl/llvm-libc++* sources/cxx-stl/system/ sources/cxx-stl/stlport && \
     cd platforms && ls | grep -v android-21 | xargs rm -Rf && \
-    cd /root/lib/android-sdk/tools && rm -Rf emulator* lib* proguard templates
+    cd /home/builder/lib/android-sdk/tools && rm -Rf emulator* lib* proguard templates
+
+# We expect this to be mounted with '-v $PWD:/home/builder/termux-packages':
+WORKDIR /home/builder/termux-packages
 

scripts/run-docker.sh

@@ -1,10 +1,6 @@
 #!/bin/sh
 set -e -u
 
-# Read settings from .termuxrc if existing
-test -f $HOME/.termuxrc && . $HOME/.termuxrc
-: ${TERMUX_TOPDIR:="$HOME/.termux-build"}
-
 IMAGE_NAME=termux/package-builder
 CONTAINER_NAME=termux-package-builder
 
@@ -15,14 +11,14 @@ docker start $CONTAINER_NAME > /dev/null 2> /dev/null || {
 	docker run \
 		-d \
 		--name $CONTAINER_NAME \
-		-v $PWD:/root/termux-packages \
+		-v $PWD:/home/builder/termux-packages \
 		-t $IMAGE_NAME
 }
 
 if [ "$#" -eq  "0" ]; then
-	docker exec -it $CONTAINER_NAME bash
+	docker exec -i -t -u builder $CONTAINER_NAME bash
 else
-	docker exec -it $CONTAINER_NAME $@
+	docker exec -i -t -u builder $CONTAINER_NAME $@
 fi