fix: have benchmark test clean working directory

Before checking out different commits, clean the working directory to
avoid checkout failures to to temporary files created during benchmark
execution (as is done by linux-loader)

Signed-off-by: Patrick Roy <roypat@amazon.co.uk>

integration_tests/test_benchmark.py

@@ -101,14 +101,21 @@ def _run_critcmp():
     print(p.stderr.decode("utf-8"))
 
 
+def _clean_workdir():
+    subprocess.run("git restore .", shell=True, check=True)
+    subprocess.run("git clean -fd", shell=True, check=True)
+
+
 def _git_checkout_upstream_branch():
     subprocess.run(
         "git fetch {} {}".format(REMOTE, BASE_BRANCH), shell=True, check=True
     )
+    _clean_workdir()
     subprocess.run("git checkout FETCH_HEAD", shell=True, check=True)
 
 
 def _git_checkout_pr_branch():
+    _clean_workdir()
     subprocess.run(
         "git checkout -",
         shell=True,