[Github] Add sccache to CI container (#122063)

This patch adds sccache to the CI container so that the
llvm-project-tests workflow does not fail due to missing sccache.

Author: boomanaiden154

.github/workflows/containers/github-action-ci/Dockerfile

@@ -67,6 +67,16 @@ RUN apt-get update && \
     file \
     tzdata
 
+# Install sccache as it is needed by most of the project test workflows and
+# cannot be installed by the ccache action when executing as a non-root user.
+# TODO(boomanaiden154): This should be switched to being installed with apt
+# once we bump to Ubuntu 24.04.
+RUN curl -L 'https://github.com/mozilla/sccache/releases/download/v0.7.6/sccache-v0.7.6-x86_64-unknown-linux-musl.tar.gz' > /tmp/sccache.tar.gz && \
+    echo "2902a5e44c3342132f07b62e70cca75d9b23252922faf3b924f449808cc1ae58 /tmp/sccache.tar.gz" | sha256sum -c && \
+    tar xzf /tmp/sccache.tar.gz -O --wildcards '*/sccache' > '/usr/local/bin/sccache' && \
+    rm /tmp/sccache.tar.gz && \
+    chmod +x /usr/local/bin/sccache
+
 ENV LLVM_SYSROOT=$LLVM_SYSROOT
 ENV PATH=${LLVM_SYSROOT}/bin:${PATH}