Compile GPU.cc files only if cuda is available

Author: smuzaffar

CondFormats/HcalObjects/BuildFile.xml

@@ -10,8 +10,12 @@
 <use name="FWCore/MessageLogger"/>
 <use name="FWCore/Utilities"/>
 <use name="Geometry/CaloTopology"/>
-<use name="HeterogeneousCore/CUDACore"/>
-<use name="HeterogeneousCore/CUDAUtilities"/>
+<iftool name="cuda">
+  <use name="HeterogeneousCore/CUDACore"/>
+  <use name="HeterogeneousCore/CUDAUtilities"/>
+<else/>
+  <flags SKIP_FILES="%GPU.cc"/>
+</iftool>
 <use name="HeterogeneousCore/AlpakaCore"/>
 <use name="HeterogeneousCore/AlpakaInterface"/>
 <flags ALPAKA_BACKENDS="1"/>