Newer macOS versions can't run 32 bit code and so the compiler, as far as I know, won't build 32 bit versions. If you are running macOS 10.15, which I believe you are, you cannot build for 32 bit anymore.

As a result, pd-lib-builder was updated to only build for the default system, in your case 64 bit, and requires an additional flag or argument to do fat builds: 

https://github.com/pure-data/pd-lib-builder/issues/50

In any case, you may have to move to a dedicated build machine which stays on an older version of macOS, say 10.14, if you personal machine is to run the latest version.

On Oct 18, 2020, at 12:00 PM, pd-list-request@lists.iem.at wrote:

Message: 1
Date: Sat, 17 Oct 2020 21:21:19 -0300
From: Alexandre Torres Porres <porres@gmail.com>
To: Pd-List <pd-list@lists.iem.at>
Subject: [PD] compiling extenrals for mac 32 bits
Message-ID:
<CAEAsFmi=3p7NLYza7v_QVb7UNj52_3Zbf-U7T-PSMWsaQkoNyw@mail.gmail.com>
Content-Type: text/plain; charset="utf-8"

Hi, I see my libraries are only available for mac 64 bits. I have the
impression it used to be also available for mac 32 bits when I compiled
them long ago, by the way. And what I mean by this is that the same
binaries could run on both.

Well, I'm using Pd lib builder and I wonder if any of you can help me on
what I should do. I don't mind doing two separate compilations, one for
each.

--------
Dan Wilcox
@danomatika
danomatika.com
robotcowboy.com