Switch OS X to 5.7

.travis.yml

@@ -115,7 +115,7 @@ install:
 
   # osx dependencies: qt, gstreamer, gstreamer-devel
   - if [ "${SPEC}" = "macx-clang" ]; then
-        wget https://s3-us-west-2.amazonaws.com/qgroundcontrol/dependencies/Qt5.8.0-mac-clang-min.tar.bz2 &&
+        wget https://s3-us-west-2.amazonaws.com/qgroundcontrol/dependencies/Qt5.7.1-mac-clang-min.tar.bz2 &&
         tar jxf Qt5.8.0-mac-clang-min.tar.bz2 -C /tmp &&
         wget https://s3-us-west-2.amazonaws.com/qgroundcontrol/dependencies/gstreamer-1.0-1.5.2-x86_64.pkg &&
         sudo installer -verboseR -pkg gstreamer-1.0-1.5.2-x86_64.pkg -target / &&
@@ -123,7 +123,7 @@ install:
         sudo installer -verboseR -pkg gstreamer-1.0-devel-1.5.2-x86_64.pkg -target / &&
         wget https://s3-us-west-2.amazonaws.com/qgroundcontrol/dependencies/osx-gstreamer.tar.bz2 &&
         sudo tar jxf osx-gstreamer.tar.bz2 -C /Library/Frameworks &&
-        export QT_DIR=Qt5.8-mac-clang/5.8/clang_64 &&
+        export QT_DIR=Qt5.7-mac-clang/5.7/clang_64 &&
         export QT_QPA_PLATFORM_PLUGIN_PATH=/tmp/$QT_DIR/plugins &&
         export QML2_IMPORT_PATH=/tmp/$QT_DIR/qml &&
         export PATH=/tmp/$QT_DIR/bin:$PATH