copy onelab.py in build dir


git-svn-id: https://geuz.org/svn/gmsh/trunk@17364 59c8cabf-10d6-4a28-b43f-3936b85956c4
don't use label if not necessary


git-svn-id: https://geuz.org/svn/gmsh/trunk@17365 59c8cabf-10d6-4a28-b43f-3936b85956c4