Seen on #43652 and #43732, happens during LLVM compilation. Error log will contain something like: ``` ERROR:sccache::server: ["ARMFastISel.cpp.o"] fatal error: Error(Io(Error { repr: Custom(Custom { kind: Other, error: StringError("Invalid checksum") }) }), State { next_error: None }) ``` cc mozilla/sccache#171.