Use BinaryBuilder.jl to package dependencies

I have tried three times to install the GMT dependency for GMT.jl and so far have not been successful. On my first try, the version of GMT in the package repos of my OS (MX Linux/Debian) was too old (v5.4). Then I attempted to build GMT from source and ran into other issues regarding (I think) GDAL, which was also an older version (v2.3). Finally, on my new OS (Ubuntu 20.04) I have GMT version 6.0.0 and GDAL version 3.0.4, but trying to run the GMT tests gives me the following error message:

ERROR: LoadError: LoadError: could not load library "/usr/lib/x86_64-linux-gnu/libgmt.so"
/home/michael/.local/julia-1.5.2/bin/../lib/julia/libstdc++.so.6: version `GLIBCXX_3.4.26' not found (required by /lib/libgdal.so.26)

Note, each time I did end up with a working version of GMT, and the only problem appears be with GMT.jl reading the dependencies.

It would be hugely beneficial for users if GMT.jl to use BinaryBuilder.jl to ship GMT and its other dependencies with the code. This would greatly simplify the process for interested users.