Travis update (#81)

* fix osx travis build

.travis.yml

@@ -25,13 +25,11 @@ addons:
       - librtaudio-dev
 
 before_script:
-  - if [ "$TRAVIS_OS_NAME" = "osx" ]; then 
-      # manually install brew packages as addon: homebrew is broken in the default osx image
-      brew install $PKGS_OSX;
-      # mac: workaround for homebrew qmake not being symlinked into $PATH
-      # see https://stackoverflow.com/questions/48847505/why-cant-i-use-qmake-on-mac-after-installing-it
-      export PATH="/usr/local/opt/qt/bin:$PATH";
-    fi
+  # manually install brew packages as addon: homebrew is broken in the default osx image
+  - if [ "$TRAVIS_OS_NAME" = "osx" ]; then HOMEBREW_NO_AUTO_UPDATE=1 brew install $PKGS_OSX; fi
+  # mac: workaround for homebrew qmake not being symlinked into $PATH
+  # see https://stackoverflow.com/questions/48847505/why-cant-i-use-qmake-on-mac-after-installing-it
+  - if [ "$TRAVIS_OS_NAME" = "osx" ]; then export PATH="/usr/local/opt/qt/bin:$PATH"; fi
 
 script: 
   - cd src