message: Fix Gitlab reports: use upstream master
diff: #!/bin/sh
  -git checkout origin/master
  +git remote add upstream https://gitlab.redox-os.org/redox-os/ion.git
  +git fetch upstream
  +git checkout upstream/master
  cargo bench
  cargo build --release
  PREV_SIZE=$(ls -al target/release/ion | cut -d' ' -f5)
  -git reset --hard HEAD
  +
  +git stash push
  git checkout -
  cargo bench
  cargo build --release
  @@ -68,4 +71,4 @@ $result
  echo $result > target/report.xml
  -exit $(test "$total_worse" -eq "0"; echo $?)
  +test "$total_worse" -eq "0"
  