$ g++-15 --version
g++-15 (Ubuntu 15.2.0-1ubuntu1) 15.2.0
$ cmake .. -GNinja -DCMAKE_CXX_COMPILER=g++-15 -DFLUX_BUILD_MODULE=On
-- The CXX compiler identification is GNU 15.2.0
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done