Skip CUDA-related tests if no GPU is present (#252)

Make unit tests that require a CUDA device skip the test and exit
succesfully if the CUDA runtime is not available, or no CUDA devices
are available.

RecoLocalTracker/SiPixelClusterizer/test/BuildFile.xml

@@ -36,13 +36,15 @@
   <use name="cuda"/>
   <use name="cub"/>
   <use name="cuda-api-wrappers"/>
+  <use name="HeterogeneousCore/CUDAUtilities"/>
   <flags CXXFLAGS="-g"/>
 </bin>
 
 <bin file="gpuClustering.cu" name="gpuClustering_debug">
   <use name="cuda"/>
   <use name="cub"/>
   <use name="cuda-api-wrappers"/>
+  <use name="HeterogeneousCore/CUDAUtilities"/>
   <flags CXXFLAGS="-g -DGPU_DEBUG"/>
   <flags CUDA_FLAGS="-g -DGPU_DEBUG"/>
 </bin>