[tlbuild] PostScript support in dvisvgm for darwin(legacy)

[Mojca Miklavec]

Dear Martin,

On 15 March 2018 at 14:26, Martin Gieseking wrote:
> Am 15.03.2018 um 12:13 schrieb Mojca Miklavec:
>>
>> Jean-François asked me if I could link dvisvgm in TeX Live against
>> libgs. Linux binaries apparently work out of the box, while mac (at
>> least the legacy ones) binaries currently require manually specifying
>> the path to the library (which works, but causes some inconvenience
>> when calling).
>
> If you don't link libgs directly, dvisvgm tries to dlopen the library.
> Therefore, libgs must be located in a directory that is part of the ld
> search path. Otherwise, it's necessary to specify the location via
> command-line option --libgs or environment variable LIBGS. It's almost the
> same on Windows except that the Ghostscript DLL is looked up through the
> executable's search PATH.

How could I add some path to the search path (on macOS)?
The --libgs flag apparently helps, but it's annoying to have to
specify it each time when the user wants to run dvisvgm.
Not that this would always help, but we could at least add the default
path of MacPorts and HomeBrew (the one from HomeBrew might already
work out of the box, I'm not eager to check right now though).

> Since I don't have access to a Mac, I can't really tell anything reliable
> about that system, but if it's possible to add /opt/local/lib/ to the search
> path of the dynamic linker, everything should work without the need to link
> libgs to dvisvgm.

Can you please point me to the code that searches for the library? I
would like to have a minimum (non)working example, so that I can
potentially ask others for help or at least experiment with super
simple and fast commands.

Thank you,
    Mojca