incorporate streetster's suggestions

Dockerfile

@@ -1,13 +1,26 @@
-FROM ubuntu:latest
+FROM ubuntu:18.04 as build
 
-RUN apt update
-RUN apt install -y wget build-essential pkg-config git binutils-mips-linux-gnu python3 zlib1g-dev libaudiofile-dev bsdmainutils
+RUN apt-get update && \
+    apt-get install -y \
+        binutils-mips-linux-gnu \
+        bsdmainutils \
+        build-essential \
+        libaudiofile-dev \
+        pkg-config \
+        python3 \
+        wget \
+        zlib1g-dev
 
-RUN wget https://github.com/n64decomp/qemu-irix/releases/download/v2.11-deb/qemu-irix-2.11.0-2169-g32ab296eef_amd64.deb
-RUN dpkg -i qemu-irix-2.11.0-2169-g32ab296eef_amd64.deb
+RUN wget \
+        https://github.com/n64decomp/qemu-irix/releases/download/v2.11-deb/qemu-irix-2.11.0-2169-g32ab296eef_amd64.deb \
+        -O qemu.deb && \
+    echo 8170f37cf03a08cc2d7c1c58f10d650ea0d158f711f6916da9364f6d8c85f741 qemu.deb | sha256sum --check && \
+    dpkg -i qemu.deb && \
+    rm qemu.deb
 
 RUN mkdir /sm64
 WORKDIR /sm64
 ENV PATH="/sm64/tools:${PATH}"
 
-CMD echo 'usage: docker run --rm --mount type=bind,source="$(pwd)",destination=/sm64 sm64 make VERSION=<version> -j4'
+CMD echo 'usage: docker run --rm --mount type=bind,source="$(pwd)",destination=/sm64 sm64 make VERSION=${VERSION:-us} -j4\n' \
+         'see https://github.com/n64decomp/sm64/blob/master/README.md for advanced usage'

README.md

@@ -38,7 +38,7 @@ To build we simply have to mount our local filesystem into the docker container
 docker run --rm --mount type=bind,source="$(pwd)",destination=/sm64 sm64 make VERSION=us -j4
 
 # if your host system is linux you need to tell docker what user should own the output files
-docker run --rm --mount type=bind,source="$(pwd)",destination=/sm64 --user "$(id -u):$(id -g)" sm64 make VERSION=us -j4
+docker run --rm --mount type=bind,source="$(pwd)",destination=/sm64 --user $UID:$UID sm64 make VERSION=us -j4
 ```
 
 Resulting artifacts can be found in the `build` directory.