Travis: Update Homebrew/fix Mac CI build

Updating Homebrew wasn't necessary when the CI build first started using
the xcode8.3 image (see c8e52741fdb623698a27a4c55cf63db93c95aa14), but
apparently it now is.

diff --git a/.travis.yml b/.travis.yml
index 94e758925321f723d7ef8e34c5becf689136346b..04eff2c0895e55d3f8bf68a3fd0abf6bc265d6ae 100644 (file)
--- a/.travis.yml
+++ b/.travis.yml
@@ -55,6 +55,7 @@ matrix:
 addons:
   homebrew:
     brewfile: true
+    update: true
 
 before_install:
   - if [ "$TRAVIS_OS_NAME" = "osx" ]; then