Dear @jorge.sampaio
I seems that the Makefile is trying to use clang instead of g++ from MacPorts.
In a new Terminal, in the directory flair-geoviewer-3.3, could you please run the following command?
make print-CXX
The expected output is:
CXX = g++
Then check which g++ is installed on your machine with the following command:
g++ -v
If this is not from MacPorts, please ensure that your PATH environment variable includes the directory where MacPort is installed, normally /opt/local/bin/
Please let us know.
Best, Luigi
P.S. Important! At moment, it is not recommended to upgrade to macOS Sequoia as FLUKA is not running on it (see this post for more info).