[Travis] Print the dcmtk cmake cache

.travis.yml

@@ -24,4 +24,5 @@ after_script:
   - ls -l /tmp/CTK-Superbuild-Release-experimental/CMakeExternals/Install/lib
   - chrpath -l /tmp/CTK-Superbuild-Release-experimental/CMakeExternals/Install/bin/storescu
   - cat /tmp/CTK-Superbuild-Release-experimental/DCMTK-build/dcmnet/apps/cmake_install.cmake
+  - cat /tmp/CTK-Superbuild-Release-experimental/DCMTK-build/CMakeCache.txt
   - "cat ~/.xpra/*"