Can't run a simulation with PLUMED

A user on the forum reported that they can't run a simulation using PLUMED even though no errors occurred during configuration (see this post). I'm able to reproduce the issue using GROMACS 2025.0 and PLUMED 2.9.

Configuring with cmake .. -DGMX_USE_PLUMED=ON, export PLUMED_KERNEL=<path-to-plumed>/lib/libplumedKernel.so, and running a simulation with gmx mdrun -plumed plumed.dat as per the reference manual gives the error

Program:     gmx mdrun, version 2025.0
Source file: src/gromacs/applied_forces/plumed/plumedMDModule_stub.cpp (line 81)
Function:    gmx::{anonymous}::PlumedMDModule::subscribeToSimulationSetupNotifications(gmx::MDModulesNotifiers*)::<lambda(const gmx::PlumedInputFilename&)>

Error in user input:
GROMACS is not compiled with the PLUMED interface, if you want to use -plumed
option, please reconfigure GROMACS with -DGMX_USE_PLUMED=ON.

For more information and tips for troubleshooting, please check the GROMACS
website at https://manual.gromacs.org/current/user-guide/run-time-errors.html
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indicating that GROMACS was compiled with the stub implementation instead of the actual plumed interface.

We should make sure that CMake correctly issues a fatal error if it's not able to create the interface when it was asked to, or in case more steps are needed to correctly build with PLUMED support, that we document them properly in the installation guide.