Use clang-format-9 for Travis CI formatting checks (#736)

.travis.yml

@@ -7,7 +7,12 @@ os:
 jobs:
   include:
   - os: linux
+    dist: bionic
     env: JOB_CHECK_FORMAT=1
+    addons:
+        apt:
+          packages:
+            - clang-format-9
   - os: linux
     env: JOB_ARCHITECTURE=arm
   - os: linux

check-format.sh

@@ -1,7 +1,10 @@
 #!/usr/bin/env bash
 
 # Run git-clang-format to check for violations
-CLANG_FORMAT_OUTPUT=$(git-clang-format --diff origin/master --extensions c,cpp,h,hpp)
+if [ "$TRAVIS" == "true" ]; then
+    EXTRA_OPTS="--binary `which clang-format-9`"
+fi
+CLANG_FORMAT_OUTPUT=$(git-clang-format --diff origin/master --extensions c,cpp,h,hpp $EXTRA_OPTS)
 
 # Check for no-ops
 grep '^no modified files to format$' <<<"$CLANG_FORMAT_OUTPUT" && exit 0