build: fix bindgen warnings breaking TravisCI

When rustfmt is missing, bindgen puts anything on one line. Any warnings then
dump so many logs that TravisCI is overwhelmed. The fix is to add rustfmt to the
environment.

See rust-lang/rust-bindgen#1600

Author: Daniel Dulaney

.travis.yml

@@ -16,10 +16,12 @@ addons:
       - build-essential
 dist: bionic
 before_install:
+  # Without rustfmt, bindgen puts everything on one line and any warnings dump so many logs they break Travis
+  # See https://github.com/rust-lang/rust-bindgen/issues/1600
+  - rustup component add rustfmt
   - if [[ $TRAVIS_OS_NAME == 'linux' ]]; then sudo apt-get install yasm; fi
   - if [[ $TRAVIS_OS_NAME == 'osx' ]]; then brew update; fi
   - if [[ $TRAVIS_OS_NAME == 'osx' ]]; then brew install yasm; fi
-  - rustup component add rustfmt
 
 script: |
     travis_wait cargo build --verbose --features "build"