Flow_meter was moved to https://github.com/CESNET/ipfixprobe
To build it as a NEMEA module, configure it using --with-nemea, e.g.:
git clone https://github.com/CESNET/ipfixprobe
cd ipfixprobe
autoreconf -i
./configure --with-nemea
make
sudo make install
Note: because of backward compatibility, we install a symlink flow_meter
into $bindir, i.e., /usr/bin/nemea/flow_meter by default; it points to
/usr/bin/ipfixprobe (default path of installed ipfixprobe).