Set Rust runtime to MSVC on Windows

.travis.yml

@@ -15,8 +15,11 @@ before_script:
   - rustup update
   - rustup component add clippy
   - rustup component add rustfmt
-  # CMake doesn't like `sh.exe` being on the PATH,
+  # CMake doesn't like the `sh.exe` provided by Git being in PATH
   - if [[ "$TRAVIS_OS_NAME" == "windows" ]]; then rm "C:/Program Files/Git/usr/bin/sh.exe"; fi
+  # MinGW doesn't implement the `poll` functions we need, so default to MSVC
+  # TODO: Attempt compilation with MSYS on Travis
+  - if [[ "$TRAVIS_OS_NAME" == "windows" ]]; then rustup default stable-x86_64-pc-windows-msvc; fi
 
 script:
   - cargo clippy --all