```cmake
option(ITK_USE_SYSTEM_GOOGLETEST "Use an outside build or install \
source of GoogleTest. Set GTEST_ROOT to specify location." ${ITK_USE_SYSTEM_LIBRARIES})
mark_as_advanced(ITK_USE_SYSTEM_GOOGLETEST)
```

Use single line for string argument, by-pass multi-line issues
user
```cmake
option(ITK_USE_SYSTEM_GOOGLETEST "Use an outside build or installed source of GoogleTest. Set GTEST_ROOT to specify location." ${ITK_USE_SYSTEM_LIBRARIES})
mark_as_advanced(ITK_USE_SYSTEM_GOOGLETEST)
```
assistant