Welcome!
Good, but there’s nothing to compile from source here 
You’re running the command julia --project, so you’re activating a local environment?
Are you on an air-gapped system? That complicates things a bit.
Are you sure you typed mpiexecc correctly? That’s an unusual name. In any case, if you want to specify a different MPI launcher executable you can pass the mpiexec keyword argument to use_system_binary:
MPIPreferences.use_system_binary(; mpiexec="mpiexecc")
or
MPIPreferences.use_system_binary(; mpiexec="/usr/local/bin/mpiexecc")
if you really want to specify the absolute path of the executable, instead of relying on it being the first one to be found in PATH. Same for libmpi: libmpi is the correct basename to dlopen /usr/local/lib/libmpi.so, if that’s the first libmpi that the dynamical linker would find, but if you want to specify the absolute path to be absolutely clear you can do it:
MPIPreferences.use_system_binary(; library_names=["/usr/local/lib/libmpi.so"])
Note that nothing is building a new OpenMPI, what the package manager is trying to do is to download a Julia package which is a thin wrapper around OpenMPI, so your worry is ill-posed.
But now we’re back to the question above: do you have access to the Internet at all?
Side note, since you’re new here: it’d be extremely helpful if you quoted the code that you copy here with triple backquotes, like this:
```
put
some
code
here
```
which you can achieve also by selecting the code and clicking the </> button in the editing toolbar. You may also want to read Please read: make it easier to help you.