Can't build with RelWithDebInfo

If I build with `colcon ...  -DCMAKE_BUILD_TYPE=RelWithDebInfo`, there is a build error:

```
--- stderr: rmw_ecal_proto_cpp
CMake Error in CMakeLists.txt:
  IMPORTED_LOCATION not set for imported target "rmw::rmw" configuration
  "RelWithDebInfo".
```
I have to use `-DCMAKE_BUILD_TYPE=Release` to pass building.