Build/Test tools: Don't attempt to report PHP's extensions when running HHVM jobs on Travis. It doesn't work.

git-svn-id: https://develop.svn.wordpress.org/trunk@40267 602fd350-edb4-49c9-b593-d223f7449a82

.travis.yml

@@ -72,7 +72,10 @@ before_script:
 - mysql --version
 - phpenv versions
 - php --version
-- php -m
+- |
+  if [[ "$TRAVIS_PHP_VERSION" != 'hhvm' ]]; then
+    php -m
+  fi
 - npm --version
 - node --version
 - phpunit --version