[Fix] build: Travis: Do not try to install xz on macOS because it is …

…already installed by travis.

git-svn-id: https://source.openmpt.org/svn/openmpt/trunk/OpenMPT@12653 56274372-70c3-4bfc-bfc3-4c3a0b034d27

.travis.yml

@@ -21,7 +21,7 @@ before_install:
   - if [[ "$TRAVIS_OS_NAME" == "linux" ]]; then sudo apt-get -qq update ; fi
   - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then brew update ; fi
   - if [[ "$TRAVIS_OS_NAME" == "linux" ]]; then sudo apt-get install -y zip unzip p7zip xz-utils make binutils gcc g++ clang tcc pkg-config help2man doxygen autoconf autoconf-archive automake libtool ccache zlib1g-dev libmpg123-dev libogg-dev libvorbis-dev portaudio19-dev libpulse-dev libflac-dev libsndfile1-dev libltdl-dev ; fi
-  - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then brew install p7zip xz help2man doxygen autoconf-archive mpg123 libogg libvorbis portaudio flac libsndfile ; fi
+  - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then brew install p7zip help2man doxygen autoconf-archive mpg123 libogg libvorbis portaudio flac libsndfile ; fi
 
 install:
   - true