Fix Android cross-compile build`cargo build --target armv7-linux-an…

[joejune]

Cross-compiling this crate for android currently fails; here is the command I am using to build:

cargo build --target armv7-linux-androideabi

This PR resolves that build failure.

To try this out, be sure to:

• Have the Android NDK configured with the toolchain available on your PATH.
• Install the target via rustup target install armv7-linux-androideabi

[danburkert]

This has been merged into master with a small tweak. Thanks!