Add Ubuntu 20.04 arm64 support (#1056)

src/ubuntu/20.04/Dockerfile

@@ -30,9 +30,10 @@ RUN apt-get update \
 # .NET SDK MSBuild requires US.UTF-8 locale to execute tasks
 RUN locale-gen en_US.UTF-8
 
-# Install Azure CLI
-RUN curl -L -o azure-cli_focal_all.deb https://aka.ms/InstallAzureCliFocalEdge \
-    && dpkg -i azure-cli_focal_all.deb
+# Install Azure CLI - https://learn.microsoft.com/en-us/cli/azure/install-azure-cli-linux?pivots=apt#option-1-install-with-one-command
+RUN curl -sL https://aka.ms/InstallAzureCLIDeb | bash \
+    # Install script does apt-get update and install, so we need to clean up after it.
+    && rm -rf /var/lib/apt/lists/*
 
 # Runtime dependencies
 RUN apt-get update \

src/ubuntu/manifest.json

@@ -96,7 +96,7 @@
         {
           "platforms": [
             {
-              "dockerfile": "src/ubuntu/20.04/amd64",
+              "dockerfile": "src/ubuntu/20.04",
               "os": "linux",
               "osVersion": "focal",
               "tags": {
@@ -109,6 +109,21 @@
             }
           ]
         },
+        {
+          "platforms": [
+            {
+              "architecture": "arm64",
+              "dockerfile": "src/ubuntu/20.04",
+              "os": "linux",
+              "osVersion": "focal",
+              "tags": {
+                "ubuntu-20.04-arm64-$(System:TimeStamp)-$(System:DockerfileGitCommitSha)": {},
+                "ubuntu-20.04-arm64$(FloatingTagSuffix)": {}
+              },
+              "variant": "v8"
+            }
+          ]
+        },
         {
           "platforms": [
             {