Use OSX CI and Windows to test other toolchains

.travis.yml

@@ -1,23 +1,31 @@
-sudo: false
+matrix:
+  include:
+    - os: linux
+      dist: bionic
       language: cpp
-compiler:
-  - gcc
-  - clang
-addons:
-  apt:
-    sources:
-    - ubuntu-toolchain-r-test
-    - llvm-toolchain-trusty-5.0
-    packages:
-    - g++-7
-    - clang-5.0
-env:
-- CXXFLAGS="-std=c++17"
+      compiler: gcc
+    - os: osx
+      osx_image: xcode10.2
+      language: cpp
+      compiler: clang
+    - os: windows
+      language: bash
+      env: CXX=cl.exe
 install:
-- "[ $CXX = g++ ] && export CXX=g++-7 || true"
-- "[ $CXX = clang++ ] && export CXX=clang++-5.0 || true"
+  - |
+    if [[ $TRAVIS_OS_NAME == 'windows' ]]; then
+      choco install ninja cmake
+    elif [[ $TRAVIS_OS_NAME == 'osx' ]]; then
+      export PATH=~/Library/Python/3.7/bin:$PATH
+      pip3 install --user ninja cmake
+    else
+      pip install --user ninja cmake
+    fi
 script:
-  - cd test
-  - mkdir build && cd build
-  - cmake ../. 
-  - make && ./tests
+  - |
+    if [[ $TRAVIS_OS_NAME == 'windows' ]]; then
+      cmd.exe /C '"C:\Program Files (x86)\Microsoft Visual Studio\2017\BuildTools\VC\Auxiliary\Build\vcvarsall.bat" amd64 && cmake -Bbuild -G Ninja -DCMAKE_BUILD_TYPE=Release -DARGPARSE_BUILD_TESTS=ON && ninja -C build'
+    else
+      cmake -Bbuild -G Ninja -DCMAKE_BUILD_TYPE=Release -DARGPARSE_BUILD_TESTS=ON && ninja -C build
+    fi
+  - ./build/test/tests