message: In travis CI, changed "exit" to conditional skip, to allow
  for updating the cache
diff: @@ -79,6 +79,7 @@ before_script:
  - if ! test -d ${ITK_BUILD_DIR}; then mkdir ${ITK_BUILD_DIR}; fi
  script:
  + - SKIP_RTK_BUILD=false
  - cd ${ITK_BUILD_DIR}
  - if ! test -e ${ITK_BUILD_DIR}/Makefile; then cmake ${ITK_SOURCE_DIR}
  -DCMAKE_BUILD_TYPE=Release
  @@ -90,7 +91,8 @@ script:
  -DITK_USE_SYSTEM_FFTW=ON
  -DUSE_FFTWD=ON
  -DUSE_FFTWF=ON
  - -DUSE_SYSTEM_FFTW=ON; make --jobs=$NUM_THREADS --keep-going; exit; fi
  + -DUSE_SYSTEM_FFTW=ON; make --jobs=$NUM_THREADS --keep-going; SKIP_RTK_BUILD=true; fi
  + - if ! test $SKIP_RTK_BUILD == true; then
  - cd $HOME
  - if ! test -d build; then mkdir build; fi
  - cd $HOME/build
  @@ -100,3 +102,4 @@ script:
  - if test $TRAVIS_OS_NAME == linux ; then make StyleCheckCode; fi
  - make --jobs=$NUM_THREADS --keep-going all
  - if test [ "$TESTING" == ON ] && [ "$CUDA" == NONE ]; then make test; fi
  + - fi
  