cargo: rustc can't find dependencies when building in a VirtualBox shared drive on a Windows VM

Similar to this old issue: https://github.com/rust-lang/rust/issues/21771

I have this main.rs:

extern crate libc;
fn main() {}

And this Cargo.toml:

[package]
name = "hello_world"
version = "0.1.0"
[dependencies]
libc = "*"

cargo build works fine on Linux. But on Windows, I get an error like this:

   Compiling libc v0.2.15
   Compiling hello_world v0.1.0 (file:///E:/hello_world)
src\main.rs:1:1: 1:19 error: use of unstable library feature 'libc': use `libc`
from crates.io (see issue #27783)
src\main.rs:1 extern crate libc;
              ^~~~~~~~~~~~~~~~~~
error: aborting due to previous error
error: Could not compile `hello_world`.

It looks like it’s building libc from crates.io, but it’s not linking against it or something? I can see a similar error on Linux if I remove the dependencies section, from Cargo.toml, which makes sense to me.

When I try different version with rustup, I see the same thing on 1.0.9, 1.0.10, and nightly.

UPDATE: I’m running all of this in a Windows 7 Virtualbox VM (Linux host), inside a shared drive. But when I try in a regular folder under C:\\, the problem goes away! Something related to shared drives?