Add helix dockerfile for CentOS Stream 9

Needed for runtime, eg dotnet/runtime#65785

src/centos/manifest.json

@@ -131,6 +131,18 @@
               }
             }
           ]
+        },
+        {
+          "platforms": [
+            {
+              "dockerfile": "src/centos/stream9/helix/amd64",
+              "os": "linux",
+              "osVersion": "centos-stream9",
+              "tags": {
+                "centos-stream9-helix-$(System:TimeStamp)-$(System:DockerfileGitCommitSha)": {}
+              }
+            }
+          ]
         }
       ]
     }

src/centos/stream9/helix/amd64/Dockerfile

@@ -0,0 +1,38 @@
+FROM quay.io/centos/centos:stream9-development
+
+# Install dependencies
+RUN dnf install --setopt tsflags=nodocs --refresh -y \
+        dnf-plugins-core \
+        epel-release \
+    && \
+    dnf config-manager --set-enabled crb \
+    && \
+    dnf install --setopt tsflags=nodocs -y \
+        gcc \
+        libicu \
+        openssl \
+        python3 \
+        python3-devel \
+        sudo \
+        tar \
+        wget \
+        which \
+    && \
+    dnf clean all
+
+RUN ln -sf /usr/bin/python3 /usr/bin/python && \
+    python -m pip install --upgrade pip==20.2 && \
+    python -m pip install virtualenv==16.6.0 && \
+    pip download --no-deps helix-scripts --index-url https://dnceng.pkgs.visualstudio.com/public/_packaging/helix-client-prod/pypi/simple && \
+    pip install ./helix_scripts-*-py3-none-any.whl
+
+ENV LANG=en_US.utf8
+
+# create helixbot user and give rights to sudo without password
+RUN /usr/sbin/adduser --uid 1000 --shell /bin/bash --gid adm helixbot && \
+    chmod 755 /root && \
+    echo "helixbot ALL=(ALL)       NOPASSWD: ALL" > /etc/sudoers
+
+USER helixbot
+
+RUN python -m virtualenv --no-site-packages /home/helixbot/.vsts-env