xlc compiler on OSX is not anymore supported.

etc/vmc/Makefile.macosxxlc

-# -*- mode: makefile -*-
-# $Id$
-
-# MacOS X with xlc platform dependent definitions
-
-# The compilers
-CXX   	  = $(shell root-config --cxx)
-CC	  = $(shell root-config --cc)
-F77	  = $(shell root-config --f77)
-
-# Global optimisation
-OPT   = -qnoopt #-g -O
-#OPT   = -O3
-
-# Shared library suffix
-SL	  = dylib
-
-#
-# The options
-#
-CXXOPTS       = $(OPT) -qpic \
-		-qflttrap=overflow:zerodivide:invalid:inexact:enable
-COPT	      = $(OPT) -qpic \
-		-qflttrap=overflow:zerodivide:invalid:inexact:enable
-FOPT	      = $(OPT) -qextname -qpic \
-		-qflttrap=overflow:zerodivide:invalid:inexact:enable
-
-# CERNLIB defines
-
-CLIBDEFS      = -DCERNLIB_LINUX -DCERNLIB_BLDLIB -DCERNLIB_CZ -DCERNLIB_PPC
-CLIBCXXOPTS   = $(CLIBDEFS)
-CLIBCOPT      = $(CLIBDEFS)
-CLIBFOPT      = $(shell echo $(CLIBDEFS) | sed -e's/-D/-WF,-D/g')
-
-LD            = export MACOSX_DEPLOYMENT_TARGET=10.3 ; unset LD_PREBIND; $(shell root-config --ld)
-LDFLAGS       = $(OPT) -bind_at_load 
-
-SHLD	      = export MACOSX_DEPLOYMENT_TARGET=10.3 ; unset LD_PREBIND; $(shell root-config --ld)
-SOFLAGS       = -dynamiclib -undefined dynamic_lookup -single_module
-SHLIB         = -lg2c
-