Configuring with benchmarks fails

Without `-DENABLE_BENCHMARKS=OFF` I'm unable to let CMake configure:
```
-- Configuring done
CMake Error at bench/CMakeLists.txt:14 (add_dependencies):
The dependency target "utrecht_tiles" of target "benchmarks" does not
exist.

CMake Error at bench/CMakeLists.txt:28 (add_dependencies):
The dependency target "utrecht_tiles" of target "benchmark-mapmatch" does
not exist.
Call Stack (most recent call first):
bench/meili/CMakeLists.txt:1 (add_valhalla_benchmark)

CMake Error at bench/CMakeLists.txt:36 (add_dependencies):
The dependency target "utrecht_tiles" of target "run-benchmark-mapmatch"
does not exist.
Call Stack (most recent call first):
bench/meili/CMakeLists.txt:1 (add_valhalla_benchmark)

CMake Error at bench/CMakeLists.txt:28 (add_dependencies):
The dependency target "utrecht_tiles" of target "benchmark-costmatrix" does
not exist.
Call Stack (most recent call first):
bench/thor/CMakeLists.txt:1 (add_valhalla_benchmark)

CMake Error at bench/CMakeLists.txt:36 (add_dependencies):
The dependency target "utrecht_tiles" of target "run-benchmark-costmatrix"
does not exist.
Call Stack (most recent call first):
bench/thor/CMakeLists.txt:1 (add_valhalla_benchmark)

CMake Error at bench/CMakeLists.txt:28 (add_dependencies):
The dependency target "utrecht_tiles" of target "benchmark-routes" does not
exist.
Call Stack (most recent call first):
bench/thor/CMakeLists.txt:2 (add_valhalla_benchmark)

CMake Error at bench/CMakeLists.txt:36 (add_dependencies):
The dependency target "utrecht_tiles" of target "run-benchmark-routes" does
not exist.
Call Stack (most recent call first):
bench/thor/CMakeLists.txt:2 (add_valhalla_benchmark)

CMake Error at bench/CMakeLists.txt:28 (add_dependencies):
The dependency target "utrecht_tiles" of target "benchmark-isochrone" does
not exist.
Call Stack (most recent call first):
bench/thor/CMakeLists.txt:3 (add_valhalla_benchmark)

CMake Error at bench/CMakeLists.txt:36 (add_dependencies):
The dependency target "utrecht_tiles" of target "run-benchmark-isochrone"
does not exist.
Call Stack (most recent call first):
bench/thor/CMakeLists.txt:3 (add_valhalla_benchmark)

CMake Error at bench/CMakeLists.txt:28 (add_dependencies):
The dependency target "utrecht_tiles" of target "benchmark-reach" does not
exist.
Call Stack (most recent call first):
bench/thor/CMakeLists.txt:4 (add_valhalla_benchmark)

CMake Error at bench/CMakeLists.txt:36 (add_dependencies):
The dependency target "utrecht_tiles" of target "run-benchmark-reach" does
not exist.
Call Stack (most recent call first):
bench/thor/CMakeLists.txt:4 (add_valhalla_benchmark)

-- Generating done
```