Install dependencies on Gentoo

Tested 24.01.2023.

Install the GMT dependencies with:

# Install required dependencies
emerge sci-libs/netcdf net-misc/curl sci-libs/gdal

# Install optional dependencies
emerge app-text/ghostscript-gpl

# to enable movie-making
emerge media-gfx/graphicsmagick media-video/ffmpeg

# to enable document viewing via gmt docs
emerge x11-misc/xdg-utils

Notes:

[...]
-- Could not find GEOS
-- Could NOT find FFTW3 (missing: FFTW3F_LIBRARY FFTW3_INCLUDE_DIR FFTW3F_VERSION_RECENT)
-- Could NOT find BLAS (missing: BLAS_LIBRARIES)
-- Could NOT find LAPACK (missing: LAPACK_LIBRARIES)
-- Could NOT find BLAS (missing: BLAS_LIBRARIES)
-- Could NOT find Sphinx (missing: SPHINX_EXECUTABLE)
[...]