Make error on Fedora 35

Cmake finds everything except IPOPT
[ 1%] Building CXX object src/lglib/CMakeFiles/lglib.dir/
lg.ypp:32:10: fatal error: config.h: No such file or directory

Installing coin-or-ipopt and coin-or-ipopt-devel using dnf satisfied the IPOPT requirement. Then I gave up on cmake and compiled and installed from source code using configure instructions in the documentation.

I could install FreeFem++ from a Fedora repository, but some functionality was missing, that’s why I needed to install from source code.