Warning in cling::IncrementalParser::CheckABICompatibility()

Cling
16

Alternatively, you can specify directly:

cmake -DCMAKE_CXX_COMPILER=/usr/local/bin/g++ -DCMAKE_C_COMPILER=/opt/gcc-4.9/bin/gcc -DCMAKE_Fortran_COMPILER=/usr/local/bin/gfortran path/to/root_src

See