fix: sanitize separators in expected path

Failed in 2h 10m
:mac: macOScurl -sS https://raw.githubusercontent.com/bazelbuild/continuous-integration/master/buildkite/bazelci.py?1736461958 -o bazelci.py && python3 bazelci.py runner --task=macos
Waited 4s
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Ran in 1h 3m
:mac: macOScurl -sS https://raw.githubusercontent.com/bazelbuild/continuous-integration/master/buildkite/bazelci.py?1736461958 -o bazelci.py && python3 bazelci.py runner --task=macos
Waited 1s
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Ran in 1h 0m
:mac: macOScurl -sS https://raw.githubusercontent.com/bazelbuild/continuous-integration/master/buildkite/bazelci.py?1736461958 -o bazelci.py && python3 bazelci.py runner --task=macos_legacy_watcher
Waited 2s
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Ran in 1h 1m
:mac: macOScurl -sS https://raw.githubusercontent.com/bazelbuild/continuous-integration/master/buildkite/bazelci.py?1736461958 -o bazelci.py && python3 bazelci.py runner --task=macos_legacy_watcher
Waited 7s
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Ran in 1h 8m
Total Job Run Time: 4h 33m