problem with parallel build on a ppc64le machine

We have been making test builds on a machine with 128 cores of the IBM ppc chip. We find that the build fails when the parallelism is too high. For instance we find this problem with, make -j128 (and sometimes with -j40):
[ 56%] Generating G__XML.cxx, ../../lib/libXMLIO_rdict.pcm, ../../lib/libXMLIO.rootmap
...
[ 57%] Built target G__ProofDraw
Error: Cannot find G__XML.cxx_tmp!
Error: Renaming G_XML.cxx_tmp into G_XML.cxx!
[ 57%] Built target G__EG
[ 57%] Built target G__XML
make[2]: *** [io/xml/G__XML.cxx] Error 1
make[2]: *** Deleting file `io/xml/G__XML.cxx'
make[1]: *** [io/xml/CMakeFiles/XMLIO.dir/all] Error 2
make[1]: *** Waiting for unfinished jobs....

There is no problem if we do not attempt a parallel build. We presume that the build dependencies are not fully specified. The failure always seems to be for io/xml/G__XML.cxx.