Travis: Add a matrix build for OS X

To guard against OS X specific issues like #1233. Do not use CircleCI as
another service here as they only offer "1 macOS container and up to 500
build minutes per month" which is far too little for our test suite
which currently takes > 20 minutes per PR (also see issue #755).

Signed-off-by: Sebastian Schuberth <sebastian.schuberth@bosch-si.com>

.travis.yml

@@ -1,11 +1,27 @@
-dist: xenial
-
-sudo: required
-
 language: java
 
-jdk:
-  - openjdk10
+env:
+  global:
+    - ANDROID_HOME="/opt/android"
+    - ANDROID_SDK_VERSION="4333796"
+    - BOWER_VERSION="1.8.8"
+    - GIMME_GO_VERSION="1.10" # Used internally by Travis.
+    - GO_DEP_VERSION="0.5.4"
+    - NPM_VERSION="6.4.0"
+    - PHP_VERSION="7.1"
+    - RUST_VERSION="1.35.0"
+    - STACK_VERSION="2.1.3"
+    - YARN_VERSION="1.17.3"
+
+matrix:
+  include:
+    - os: linux
+      dist: xenial
+      jdk: openjdk10
+      env: ANDROID_SDK_ARCHIVE="sdk-tools-linux-$ANDROID_SDK_VERSION.zip"
+    - os: osx
+      osx_image: xcode10
+      env: ANDROID_SDK_ARCHIVE="sdk-tools-darwin-$ANDROID_SDK_VERSION.zip"
 
 before_cache:
   - rm -f  $HOME/.gradle/caches/modules-2/modules-2.lock
@@ -22,38 +38,34 @@ cache:
     - $HOME/.ort/downloader/cache/http
     - $HOME/.ort/scanner/cache/http
 
-env:
-  global:
-    - ANDROID_HOME="/opt/android"
-    - ANDROID_SDK_VERSION="4333796"
-    - BOWER_VERSION="1.8.8"
-    - GIMME_GO_VERSION="1.10" # Used internally by Travis.
-    - GO_DEP_VERSION="0.5.1"
-    - NPM_VERSION="6.4.0"
-    - PHP_VERSION="7.1"
-    - RUST_VERSION="1.35.0"
-    - STACK_VERSION="2.1.3"
-    - YARN_VERSION="1.17.3"
-
 before_install:
-  - sudo rm -f $JAVA_HOME/lib/security/cacerts
-  - sudo ln -s /etc/ssl/certs/java/cacerts $JAVA_HOME/lib/security/cacerts
+  - if [ "$TRAVIS_OS_NAME" = "linux" ]; then
+      sudo rm -f $JAVA_HOME/lib/security/cacerts;
+      sudo ln -s /etc/ssl/certs/java/cacerts $JAVA_HOME/lib/security/cacerts;
+    fi
 
 install:
-  - sudo apt install -y cvs
-  - eval "$(gimme)"
-  - curl https://raw.githubusercontent.com/golang/dep/v$GO_DEP_VERSION/install.sh | sh
-  - npm install -g bower@$BOWER_VERSION npm@$NPM_VERSION yarn@$YARN_VERSION
-  - phpenv global $PHP_VERSION
-  - curl -Ls https://git.io/sbt > ~/bin/sbt
-  - chmod a+x ~/bin/sbt
+  - npm install -g bower@$BOWER_VERSION npm@$NPM_VERSION yarn@$YARN_VERSION # Need to run this before brew to avoid "dyld: Library not loaded".
+  - |
+    if [ "$TRAVIS_OS_NAME" = "linux" ]; then
+      sudo apt install -y cvs;
+      eval "$(gimme)";
+      curl https://raw.githubusercontent.com/golang/dep/v$GO_DEP_VERSION/install.sh | sh;
+      phpenv global $PHP_VERSION;
+      curl -Ls https://git.io/sbt > ~/bin/sbt;
+      chmod a+x ~/bin/sbt;
+    elif [ "$TRAVIS_OS_NAME" = "osx" ]; then
+      mkdir ~/bin;
+      brew install cvs dep@$GO_DEP_VERSION php${PHP_VERSION//./} sbt
+    fi
   - curl -sSL https://github.com/commercialhaskell/stack/raw/v$STACK_VERSION/etc/scripts/get-stack.sh | sh
   - curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y --default-toolchain $RUST_VERSION
   - export PATH=$PATH:$HOME/.cargo/bin
   - curl https://storage.googleapis.com/git-repo-downloads/repo > ~/bin/repo
   - chmod a+x ~/bin/repo
-  - curl -Os https://dl.google.com/android/repository/sdk-tools-linux-$ANDROID_SDK_VERSION.zip
-  - unzip -q sdk-tools-linux-$ANDROID_SDK_VERSION.zip -d $ANDROID_HOME
+  - curl -Os https://dl.google.com/android/repository/$ANDROID_SDK_ARCHIVE
+  - sudo unzip -q $ANDROID_SDK_ARCHIVE -d $ANDROID_HOME
+  - sudo chmod a+x $ANDROID_HOME/tools/bin/sdkmanager
   - export SDKMANAGER_OPTS="--add-modules java.xml.bind"
   - yes | $ANDROID_HOME/tools/bin/sdkmanager --verbose "platform-tools"