Unexpected short read from file (rustc.bzl)

[rejuvenile]

Every so often, when changing Cargo Bazel settings, my Bazel state is corrupted and only a bazel clean --expunge fixes it:

ERROR: @rules_rust//:extra_rustc_flags :: Error loading option @rules_rust//:extra_rustc_flags: error loading package '@@rules_rust+//rust/settings': at /mnt/fast/buildkite-agent/bob/test/external/rules_rust+/rust/settings/settings.bzl:21:5: 

Encountered error while reading extension file 'rust/private/rustc.bzl': Unexpected short read from file '/mnt/fast/buildkite-agent/bob/test/external/rules_rust+/rust/private/rustc.bzl' (expected 109683, got 109660 bytes)

This happens simultaneously across multiple build agents. The new rustc.bzl looks correct; it's not truncated.

[rejuvenile]

I also see this with cargo/private/cargo_bootstrap.bzl. I vendor rules_rust, so every so often the source does change from a pull; it's not clear if that makes a difference.