make use of 2 dedicated cores while assuming both are blocked on I/O

.travis.yml

@@ -40,7 +40,7 @@ before_script:
  - if [ "${TRAVIS_OS_NAME}" = "osx" ]; then ./CI/before_script.osx.sh; fi
 script:
  - cd ./build
- - if [ "$COVERITY_SCAN_BRANCH" != 1 ]; then ${ANALYZE}make -j2; fi
+ - if [ "$COVERITY_SCAN_BRANCH" != 1 ]; then ${ANALYZE}make -j3; fi
  - if [ "$COVERITY_SCAN_BRANCH" != 1 ] && [ "${TRAVIS_OS_NAME}" = "osx" ]; then make package; fi
  - if [ "$COVERITY_SCAN_BRANCH" != 1 ] && [ "${TRAVIS_OS_NAME}" = "linux" ]; then ./openmw_test_suite; fi
  - if [ "$COVERITY_SCAN_BRANCH" != 1 ] && [ "${TRAVIS_OS_NAME}" = "linux" ]; then cd .. && ./CI/check_tabs.sh; fi