.travis.yml: build in parallel

.travis.yml

@@ -18,9 +18,9 @@ before_install:
   - sudo apt-get install -y libgl1-mesa-dev libpulse-dev libxrandr-dev libgtk-3-dev
 
 script:
-  - make CXX="g++-5" CC="gcc-5" linux-debug64       && ./build/linux64/bin/crown-debug --run-unit-tests
-  - make CXX="g++-5" CC="gcc-5" linux-development64 && ./build/linux64/bin/crown-development --run-unit-tests
-  - make CXX="g++-5" CC="gcc-5" linux-release64     && ./build/linux64/bin/crown-release --run-unit-tests
+  - make MAKE_JOBS=4 CXX="g++-5" CC="gcc-5" linux-debug64       && ./build/linux64/bin/crown-debug --run-unit-tests
+  - make MAKE_JOBS=4 CXX="g++-5" CC="gcc-5" linux-development64 && ./build/linux64/bin/crown-development --run-unit-tests
+  - make MAKE_JOBS=4 CXX="g++-5" CC="gcc-5" linux-release64     && ./build/linux64/bin/crown-release --run-unit-tests
 
 notifications:
   email: false