Run Travis build on macOS

.travis.yml

@@ -2,6 +2,9 @@ env:
   global:
   # for CodeClimate
     - CC_TEST_REPORTER_ID=83a2e05f875e3a67f60a1969f20a558a3de03a7592052c8bf52807d0e317f01a
+os:
+- linux
+- osx
 language: java
 jdk:
 - oraclejdk8
@@ -27,24 +30,40 @@ jdk:
 #  - openjdk6 # gradle 3.1 requires java 7
 
 matrix:
+  exclude:
+  - os: macos
+    jdk: oraclejdk8
+  - os: macos
+    jdk: openjdk7
+  - os: macos
+    jdk: openjdk8
+  - os: macos
+    jdk: openjdk9
+  - os: macos
+    jdk: openjdk10
   allow_failures:
   - jdk: oraclejdk-ea
   - jdk: openjdk7
   - jdk: oraclejdk8
   - jdk: oraclejdk11
-  - jdk: openjdk15
   - jdk: openjdk-ea
     #  - openjdk7 # Disabled to avoid error java.security.NoSuchProviderException: no such provider: SunEC...
 
 install: skip
 before_script:
   - chmod +x gradlew
 # for CodeClimate
-  - curl -L https://codeclimate.com/downloads/test-reporter/test-reporter-latest-linux-amd64 > ./cc-test-reporter
-  - chmod +x ./cc-test-reporter
-  - ./cc-test-reporter before-build
+  - |
+    if [ "$TRAVIS_OS_NAME" = "linux" ]; then
+      curl -L https://codeclimate.com/downloads/test-reporter/test-reporter-latest-linux-amd64 > ./cc-test-reporter &&
+        chmod +x ./cc-test-reporter &&
+        ./cc-test-reporter before-build
+    fi
 script:
   - ./gradlew check --info --stacktrace
 after_success:
   - bash <(curl -s https://codecov.io/bash)
-  - ./cc-test-reporter after-build --exit-code $TRAVIS_TEST_RESULT
+  - |
+    if [ "$TRAVIS_OS_NAME" = "linux" ]; then
+      ./cc-test-reporter after-build --exit-code $TRAVIS_TEST_RESULT
+    fi