Fix permission denied failure in bazel CI job
Fix permission denied failure in bazel CI job

This job started failing in GitHub Actions with this error:

    ## $ bazel run demo-rs --verbose_failures --noshow_progress
    Downloading https://releases.bazel.build/3.1.0/release/bazel-3.1.0-linux-x86_64...
    could not run Bazel: could not start Bazel: fork/exec /home/runner/work/cxx/cxx/tools/bazel: permission denied
    ##[error]Process completed with exit code 1.

dtolnay/cxx,dtolnay/cxx,dtolnay/cxx,dtolnay/cxx