Remove try_run test for libXml2 again after finding bug in code.
Remove try_run test for libXml2 again after finding bug in code.

nickerso/libcellml,MichaelClerx/libcellml,cellml/libcellml,cellml/libcellml,hsorby/libcellml,hsorby/libcellml,hsorby/libcellml,cellml/libcellml,nickerso/libcellml,nickerso/libcellml,MichaelClerx/libcellml,MichaelClerx/libcellml,hsorby/libcellml,nickerso/libcellml,cellml/libcellml