macOS Sonoma / Xcode 15

[rieder]

As every year, an update on AMUSE and the new macOS/Xcode releases.
Upgrading to Xcode 15 gave me some issues with my working environment, so I recommend not doing that until you upgrade to Sonoma (and you have to).

Upgrading to Sonoma is ok - but it seems MacPorts is not yet fully ready for this (I had some build issues).
I decided to use the opportunity to check on Homebrew instead - which seems to work fine, just install using their default instructions.
Install instructions for AMUSE prerequisites (I'll add these to the documentation), with thanks to Sylvia Ekström for being a guinea pig:

brew install pkg-config
brew install gcc hdf5 netcdf cmake
brew install open-mpi --build-from-source --cc=gcc-13  # or whichever version was installed
brew install gsl gmp mpfr fftw openblas lapack

I also did the following, to make sure AMUSE and everything else uses the right GCC compilers (and not Apple's clang-masking-as-gcc):

cd /opt/homebrew/bin
ln -s gcc-13 gcc
ln -s g++-13 g++

Then AMUSE installed as it is supposed to.