CMake fixes: (#3437)

CMake fixes:
Added FindVGM.cmake to amend the target provided by VGM installation

dependencies/FindVGM.cmake

@@ -0,0 +1,31 @@
+
+# Copyright CERN and copyright holders of ALICE O2. This software is distributed
+# under the terms of the GNU General Public License v3 (GPL Version 3), copied
+# verbatim in the file "COPYING".
+#
+# See http://alice-o2.web.cern.ch/license for full licensing information.
+#
+# In applying this license CERN does not waive the privileges and immunities
+# granted to it by virtue of its status as an Intergovernmental Organization or
+# submit itself to any jurisdiction.
+
+# use the VGMConfig.cmake provided by the VGM installation but
+# amend the target VGM::XmlVGM with the include  and link directories
+
+find_package(VGM NO_MODULE)
+if(NOT VGM_FOUND)
+  return()
+endif()
+
+# VGM uses namespace since 4.7
+if(${VGM_VERSION} VERSION_LESS "4.7")
+  set(targetVGM XmlVGM)
+else()
+  set(targetVGM VGM::XmlVGM)
+endif()
+
+set_target_properties(${targetVGM}
+                      PROPERTIES INTERFACE_INCLUDE_DIRECTORIES
+                                "${VGM_INCLUDE_DIRS}"
+                      INTERFACE_LINK_DIRECTORIES
+                                $<TARGET_FILE_DIR:${targetVGM}>)

dependencies/O2SimulationDependencies.cmake

@@ -52,15 +52,20 @@ set_package_properties(Geant3
                        PROPERTIES
                        TYPE ${mcPackageRequirement} DESCRIPTION
                             "the legacy but not slow MC transport engine")
+
 find_package(Geant4 MODULE)
 set_package_properties(Geant4
                        PROPERTIES
                        TYPE ${mcPackageRequirement} DESCRIPTION
                             "more recent and more complete MC transport engine")
+
+
 find_package(Geant4VMC MODULE)
 set_package_properties(Geant4VMC PROPERTIES TYPE ${mcPackageRequirement})
-find_package(VGM CONFIG)
+
+find_package(VGM MODULE)
 set_package_properties(VGM PROPERTIES TYPE ${mcPackageRequirement})
+
 find_package(HepMC MODULE)
 set_package_properties(HepMC
 		       PROPERTIES