.bc file not found when building with --rlib

[jhasse]

~ echo '#[crate_type="rlib"];' > foo.rs
~ rustc --rlib foo.rs
error: ar rS libfoo-d4ab21d1-0.0.rlib foo.bc failed with: exit code: 1
note: stdout ---

note: stderr ---
ar: foo.bc: No such file or directory

error: aborting due to previous error
task 'rustc' failed at 'explicit failure', C:\Users\jhass_000\git\rust\src\libsyntax\diagnostic.rs:75
task '<main>' failed at 'explicit failure', C:\Users\jhass_000\git\rust\src\librustc\lib.rs:440
~ rustc foo.rs
~ ls
foo.rs  libfoo-d4ab21d1-0.0.rlib

When building with --rlib rustc can't find the bytecode file.