Added libxml2 to --pm system.

ogscm/recipes/ogs.py

@@ -237,6 +237,7 @@ if local_args.ogs != "clean":
         Stage0 += cmake(eula=True, version="3.16.6")
         Stage0 += boost(version="1.66.0", bootstrap_opts=["headers"])
         Stage0 += environment(variables={"BOOST_ROOT": "/usr/local/boost"})
+        Stage0 += packages(apt=["libxml2-dev"], yum=["libxml2-devel"])
         vtk_cmake_args = [
             "-DModule_vtkIOXML=ON",
             "-DModule_vtkIOLegacy=ON",