Merge branch 'macos_lz4' into 'master'

MacOS and LZ4

See merge request OpenMW/openmw!356

CI/before_install.osx.sh

@@ -5,5 +5,8 @@ command -v ccache >/dev/null 2>&1 || brew install ccache
 command -v cmake >/dev/null 2>&1 || brew install cmake
 command -v qmake >/dev/null 2>&1 || brew install qt
 
-curl -fSL -R -J https://downloads.openmw.org/osx/dependencies/openmw-deps-20201016.zip -o ~/openmw-deps.zip
+brew link --overwrite lz4  #  overwrite system lz4; use brew
+brew reinstall lz4
+
+curl -fSL -R -J https://downloads.openmw.org/osx/dependencies/openmw-deps-ef2462c.zip -o ~/openmw-deps.zip
 unzip -o ~/openmw-deps.zip -d /private/tmp/openmw-deps > /dev/null