[CI] Download lit timing files (llvm#160138)

This patch downloads the lit timing files from our GCS bucket into the
local directory so that lit can execute them in a smarter order (biggest
first to take advantage of parallelism).

Author: boomanaiden154

.ci/monolithic-linux.sh

@@ -32,8 +32,6 @@ enable_cir="${6}"
 lit_args="-v --xunit-xml-output ${BUILD_DIR}/test-results.xml --use-unique-output-file-name --timeout=1200 --time-tests --succinct"
 
 start-group "CMake"
-export PIP_BREAK_SYSTEM_PACKAGES=1
-pip install -q -r "${MONOREPO_ROOT}"/.ci/all_requirements.txt
 
 # Set the system llvm-symbolizer as preferred.
 export LLVM_SYMBOLIZER_PATH=`which llvm-symbolizer`

.ci/utils.sh

@@ -52,3 +52,10 @@ function start-group {
     echo "Starting $groupname"
   fi
 }
+
+export PIP_BREAK_SYSTEM_PACKAGES=1
+pip install -q -r "${MONOREPO_ROOT}"/.ci/all_requirements.txt
+
+if [[ "$GITHUB_ACTIONS" != "" ]]; then
+  python .ci/cache_lit_timing_files.py download
+fi