[cxxmodules] Resurrect cxx modules nightly builds.
[cxxmodules] Resurrect cxx modules nightly builds.

When we build with -Dcxxmodules=On we should set the cpp_module otherwise
we get an incomplete modulemap.

olifre/root,root-mirror/root,root-mirror/root,karies/root,olifre/root,zzxuanyuan/root,zzxuanyuan/root,karies/root,olifre/root,karies/root,karies/root,olifre/root,zzxuanyuan/root,root-mirror/root,karies/root,olifre/root,olifre/root,karies/root,karies/root,zzxuanyuan/root,olifre/root,zzxuanyuan/root,karies/root,root-mirror/root,root-mirror/root,zzxuanyuan/root,zzxuanyuan/root,root-mirror/root,zzxuanyuan/root,karies/root,karies/root,olifre/root,root-mirror/root,olifre/root,zzxuanyuan/root,olifre/root,zzxuanyuan/root,root-mirror/root,karies/root,olifre/root,zzxuanyuan/root,zzxuanyuan/root,root-mirror/root,root-mirror/root,root-mirror/root