MagFieldConditions: cmake cleanup, remove ROOT dependency

MagneticField/MagFieldConditions/CMakeLists.txt

-################################################################################
-# Package: MagFieldConditions
-################################################################################
+# Copyright (C) 2002-2020 CERN for the benefit of the ATLAS collaboration
 
 # Declare the package name:
 atlas_subdir( MagFieldConditions )
 
-# Declare the package's dependencies:
-atlas_depends_on_subdirs( PUBLIC
-                          Control/StoreGate
-			  GaudiKernel
-                          PRIVATE
-                          MagneticField/MagFieldElements
-                          )
-
-# External dependencies:
-find_package( ROOT COMPONENTS Core Tree MathCore Hist RIO pthread )
-
 # Component(s) in the package:
 atlas_add_library( MagFieldConditions
                    src/*.cxx
                    PUBLIC_HEADERS MagFieldConditions
-                   PRIVATE_INCLUDE_DIRS ${ROOT_INCLUDE_DIRS}
-                   LINK_LIBRARIES SGTools GaudiKernel StoreGateLib
-                   PRIVATE_LINK_LIBRARIES ${ROOT_LIBRARIES} MagFieldElements)
-
-
+                   LINK_LIBRARIES AthenaKernel GaudiKernel MagFieldElements )