GeneratorUtils: Add interface library

Generators/GeneratorUtils/CMakeLists.txt

-################################################################################
-# Package: GeneratorUtils
-################################################################################
+# Copyright (C) 2002-2020 CERN for the benefit of the ATLAS collaboration
 
 # Declare the package name:
 atlas_subdir( GeneratorUtils )
 
-# Declare the package's dependencies:
-atlas_depends_on_subdirs( PRIVATE
-                          AtlasTest/TestTools )
-
-# External dependencies:
-find_package( Boost COMPONENTS filesystem thread system )
-
 # Component(s) in the package:
+atlas_add_library( GeneratorUtilsLib
+                   GeneratorUtils/*.h
+                   INTERFACE
+                   PUBLIC_HEADERS GeneratorUtils
+                   INCLUDE_DIRS ${Boost_INCLUDE_DIRS}
+                   LINK_LIBRARIES ${Boost_LIBRARIES} )
+
+# Test(s) in the package:
 atlas_add_test( StringParse_test
                 SOURCES
                 test/StringParse_test.cxx
-                INCLUDE_DIRS ${Boost_INCLUDE_DIRS}
-                LINK_LIBRARIES ${Boost_LIBRARIES} TestTools )
+                LINK_LIBRARIES GeneratorUtilsLib )
 
 # Install files from the package:
-atlas_install_headers( GeneratorUtils )
 atlas_install_joboptions( share/*.py )
-