xAODJetCnv: cmake fixes

Define an interface library for headers exported from this package.

Event/xAOD/xAODJetCnv/CMakeLists.txt

@@ -17,14 +17,20 @@ atlas_depends_on_subdirs( PUBLIC
                           Control/StoreGate
                           Reconstruction/Jet/JetEvent )
 
+atlas_add_library( xAODJetCnvLib
+                   xAODJetCnv/*.h
+                   INTERFACE
+                   PUBLIC_HEADERS xAODJetCnv
+                   LINK_LIBRARIES GaudiKernel xAODJet xAODBase AthLinks )
+
+
 # Component(s) in the package:
 atlas_add_component( xAODJetCnv
                      src/*.cxx
                      src/components/*.cxx
-                     LINK_LIBRARIES AthLinks xAODBase xAODJet GaudiKernel AthenaBaseComps AthenaKernel StoreGateLib SGtests JetEvent )
+                     LINK_LIBRARIES xAODJetCnvLib xAODJet GaudiKernel AthenaBaseComps AthenaKernel StoreGateLib SGtests JetEvent )
 
 # Install files from the package:
-atlas_install_headers( xAODJetCnv )
 atlas_install_python_modules( python/*.py )
 atlas_install_joboptions( share/*.py )