Merge branch 'travis-ci-mac-build' into 'master'

Add a travis CI config file to run a Mac build

See merge request !622

.travis.yml

+language: cpp
+
+matrix:
+  include:
+    - os: osx
+      osx_image: xcode10.2
+      before_install:
+        - brew install eigen
+    - os: linux
+      addons:
+        apt:
+          update: true
+          sources:
+            - sourceline: 'ppa:mhier/libboost-latest'
+            - ubuntu-toolchain-r-test
+          packages:
+            - libeigen3-dev
+            - boost1.67
+            - cmake
+            - g++-7
+      env: CC=gcc-7 CXX=g++-7
+    - os: linux
+      sudo: required
+      before_install:
+        - wget --no-check-certificate https://ecsft.cern.ch/dist/cvmfs/cvmfs-release/cvmfs-release-latest_all.deb
+        - sudo dpkg -i cvmfs-release-latest_all.deb
+        - sudo apt-get update
+        - sudo apt-get install cvmfs cvmfs-config-default
+        - rm -f cvmfs-release-latest_all.deb
+        - wget --no-check-certificate https://lcd-data.web.cern.ch/lcd-data/CernVM/default.local
+        - sudo mkdir -p /etc/cvmfs
+        - sudo mv default.local /etc/cvmfs/default.local
+        - sudo /etc/init.d/autofs stop
+        - sudo cvmfs_config setup
+        - sudo mkdir -p /cvmfs/sft.cern.ch
+        - sudo mount -t cvmfs sft.cern.ch /cvmfs/sft.cern.ch
+        - ls /cvmfs/sft.cern.ch
+      services:
+        - docker
+      script:
+        - docker run -ti --name CI_container -v ${PWD}:/src -w /src -v"/cvmfs:/cvmfs:ro" -d gitlab-registry.cern.ch/acts/machines/cc7 /bin/bash
+        - docker exec -ti CI_container /bin/bash -c "source CI/setup_lcg94.sh && mkdir build && cd build && cmake .. -DACTS_BUILD_EXAMPLES=on -DACTS_BUILD_TESTS=on -DACTS_BUILD_INTEGRATION_TESTS=on -DACTS_BUILD_DIGITIZATION_PLUGIN=on -DACTS_BUILD_IDENTIFICATION_PLUGIN=on -DACTS_BUILD_JSON_PLUGIN=on -DACTS_BUILD_LEGACY=on -DACTS_BUILD_DD4HEP_PLUGIN=on -DACTS_BUILD_TGEO_PLUGIN=on && cmake --build . -- -j$(nproc) && cmake --build . -- test"
+
+script:
+  - mkdir build && cd build
+  - cmake .. -DCMAKE_CXX_FLAGS="-std=c++17" -DACTS_BUILD_EXAMPLES=on -DACTS_BUILD_TESTS=on -DACTS_BUILD_INTEGRATION_TESTS=on -DACTS_BUILD_DIGITIZATION_PLUGIN=on -DACTS_BUILD_IDENTIFICATION_PLUGIN=on -DACTS_BUILD_JSON_PLUGIN=on -DACTS_BUILD_LEGACY=on
+  - cmake --build . -- -j$(nproc)
+  - cmake --build . -- test
+
+
+
+