[macOS, CI] Build using macOS 10.13 SDK

.travis.yml

@@ -1,7 +1,7 @@
 os:
  - linux
  - osx
-osx_image: xcode8.3
+osx_image: xcode9.4
 language: cpp
 sudo: required
 dist: trusty

CI/before_install.osx.sh

@@ -6,5 +6,5 @@ brew outdated cmake || brew upgrade cmake
 brew outdated pkgconfig || brew upgrade pkgconfig
 brew install $macos_qt_formula
 
-curl https://downloads.openmw.org/osx/dependencies/openmw-deps-c40905f.zip -o ~/openmw-deps.zip
+curl https://downloads.openmw.org/osx/dependencies/openmw-deps-100d2e0.zip -o ~/openmw-deps.zip
 unzip ~/openmw-deps.zip -d /private/tmp/openmw-deps > /dev/null

CI/before_script.osx.sh

@@ -11,7 +11,7 @@ cd build
 cmake \
 -D CMAKE_PREFIX_PATH="$DEPENDENCIES_ROOT;$QT_PATH" \
 -D CMAKE_OSX_DEPLOYMENT_TARGET="10.9" \
--D CMAKE_OSX_SYSROOT="macosx10.12" \
+-D CMAKE_OSX_SYSROOT="macosx10.13" \
 -D CMAKE_BUILD_TYPE=Release \
 -D OPENMW_OSX_DEPLOYMENT=TRUE \
 -D DESIRED_QT_VERSION=5 \