Update .travis.yml

Author: dcwhite

.travis.yml

@@ -53,6 +53,7 @@ install:
 - if [[ "$TRAVIS_OS_NAME" == "linux" ]]; then sudo apt-get install mesa-common-dev libgl1-mesa-dev mesa-utils-extra libglapi-mesa ninja-build libqt4-dev qt4-qmake libqt4-opengl-dev; fi
 - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then travis_wait 30 scripts/getQt4Mac.sh; fi
 - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then brew install qt || true; fi
+- if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then brew update; fi
 - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then echo $(brew --prefix qt); fi
 - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then cd $(brew --prefix qt)/5.13.0/clang_64 || true; fi
 - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then cd $(brew --prefix qt)/5.13.1/clang_64 || true; fi