DD4hep Examples

The subfolders in this directory contain several examples on how to use DD4hep. There are two ways to build these examples:

Recommended way: to build all examples in this folder:

mkir build
cd build
cmake ..
make
make install
ctest --output-on-failure

or to build a subset, use the variable DD4HEP_BUILD_EXAMPLES e.g.

cmake -DDD4HEP_BUILD_EXAMPLES="OpticalSurfaces DDG4" ..
make
make install
ctest --output-on-failure

Not-recommended way: It is also possible to build each subfolder separately, however in this case the tests are not enabled:
```
cd OpticalSurfaces
mkir build
cd build
cmake ..
make
make install
```