Enable -fPIC in Nanos6 and NODES
Adds a test where we build a OmpSs-2 program with clang using Nanos6 and NODES.
We patch the Nanos6 release with the -fPIC
patch from master.
Adds nOS-V and NODES git too (fixed in master).
See #143 (closed) and https://gitlab.bsc.es/nos-v/nodes/-/merge_requests/17 .