Update CPU build to Ubuntu 20.04 (#1009)

Dockerfile

@@ -1,5 +1,5 @@
 # IMAGE needs be be set to one of the docker/dawn-env.dockerfile images
-ARG IMAGE=gtclang/dawn-env-ubuntu19.10
+ARG IMAGE=gtclang/dawn-env-ubuntu20.04
 FROM $IMAGE
 ARG BUILD_TYPE=Release
 COPY . /usr/src/dawn

docker/ubuntu20.04.dockerfile

@@ -0,0 +1,17 @@
+FROM ubuntu:focal
+RUN apt update && apt install -y --no-install-recommends \
+    apt-transport-https ca-certificates \
+    gnupg software-properties-common curl && apt clean
+# Add CMake repo
+RUN curl -L https://apt.kitware.com/keys/kitware-archive-latest.asc | apt-key add -
+RUN apt-add-repository 'deb https://apt.kitware.com/ubuntu/ focal main'
+RUN apt-add-repository 'deb https://apt.kitware.com/ubuntu/ focal-rc main'
+RUN apt-get install kitware-archive-keyring && apt clean
+RUN apt update && apt install -y --no-install-recommends \
+    build-essential ninja-build cmake git openssh-client curl \
+    llvm-9-dev libclang-9-dev libclang-cpp9 \
+    python3 python3-pip libpython3-dev \
+    python3-setuptools python3-wheel \
+    libboost-dev && apt clean
+RUN python3 -m pip install --upgrade pip
+RUN update-alternatives --install /usr/bin/python python /usr/bin/python3 10

docker/update-images

@@ -11,34 +11,27 @@ if [ $# -eq 0 ]; then
     usage
 fi
 
-if [ "$1" = "-s" ]; then
-    cmd_prefix="sudo"
-    shift
-else
-    cmd_prefix=""
-fi
-
 while [ "$1" != "" ]; do
     case $1 in
     c | cpu)
-        image_name=gtclang/dawn-env-ubuntu19.10
-        $cmd_prefix docker build --rm \
+        image_name=gtclang/dawn-env-ubuntu20.04
+        docker build --rm \
             --tag $image_name-base \
-            --file docker/ubuntu19.10.dockerfile .
-        $cmd_prefix docker build --rm \
+            --file docker/ubuntu20.04.dockerfile .
+        docker build --rm \
             --tag $image_name --build-arg IMAGE=$image_name-base \
             --file docker/dawn-env.dockerfile .
-        echo "Now run:\n\t$cmd_prefix docker push $image_name"
+        echo "Now run:\n\tdocker push $image_name"
         ;;
     g | gpu)
         image_name=gtclang/dawn-env-cuda10.1-ubuntu18.04
-        $cmd_prefix docker build --rm \
+        docker build --rm \
             --tag $image_name-base \
             --file docker/cuda10.1-ubuntu18.04.dockerfile .
-        $cmd_prefix docker build --rm \
+        docker build --rm \
             --tag $image_name --build-arg IMAGE=$image_name-base \
             --file docker/dawn-env.dockerfile .
-        echo "Now run:\n\t$cmd_prefix docker push $image_name"
+        echo "Now run:\n\tdocker push $image_name"
         ;;
     *)
         usage