pre-commit fails when RUNFILES_MANIFEST_FILE is set

For some reason, when running pre-commit from rules_git the RUNFILES_MANIFEST_FILE environment variable is set. This causes the lookup for a runfile folder to fail since it isn't explicitly listed in the manifest.

$ bazel run @pre-commit -- --version
(...)
  File "/data_sda/aleter01/cache/bazel/execroot/_main/bazel-out/k8-fastbuild/bin/external/pre-commit+/pre-commit/pre-commit.runfiles/_main/../pre-commit+/pre-commit/__main__.py", line 176, in <module>
    bazel, *rest = runfile("pre-commit/pre-commit/bazel").glob("bazel*")
                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/data_sda/aleter01/cache/bazel/execroot/_main/bazel-out/k8-fastbuild/bin/external/pre-commit+/pre-commit/pre-commit.runfiles/_main/../pre-commit+/pre-commit/__main__.py", line 49, in runfile
    raise RunfileNotFoundError(path)
RunfileNotFoundError: pre-commit/pre-commit/bazel