Hi @aurelien ,
that’s likely not the full error (there is no compiler or cmake error displayed). In a multi-core build -j8 the actual error message might be many lines above. Please post the result of make VERBOSE=1 -j1.
About building offline: @bellenot might be able to indicate which cmake configuration flags you should pass in order to build ROOT offline. This post might also help: Offline Build Update
Cheers,
Enrico