D3PDMakerInterfaces: cmake fixes

Define an interface library for exported headers.

PhysicsAnalysis/D3PDMaker/D3PDMakerInterfaces/CMakeLists.txt

@@ -5,10 +5,8 @@
 # Declare the package name:
 atlas_subdir( D3PDMakerInterfaces )
 
-# Declare the package's dependencies:
-atlas_depends_on_subdirs( PUBLIC
-                          GaudiKernel )
-
-# Install files from the package:
-atlas_install_headers( D3PDMakerInterfaces )
-
+atlas_add_library( D3PDMakerInterfaces
+                   D3PDMakerInterfaces/*.h
+                   INTERFACE
+                   PUBLIC_HEADERS D3PDMakerInterfaces
+                   LINK_LIBRARIES GaudiKernel )