Hmm, we need to build the OWL libraries differently.
I ran into this on my machine as well, but not sure how it gets resolved:

 In file included from LibSource/ColourScreenPatch.cpp:6:
./Source/PatchProcessor.h:5:10: fatal error: Patch.h: No such file or directory
    5 | #include "Patch.h"
      |          ^~~~~~~~~
compilation terminated.

Normally you have to run make libs, but this tries to build WASM as well which we don't want (requires emcc).
So I'm just running make -f compile.mk libs here.

We may need to patch out the web build for this.

[edit: done just that: web libs build is patched out from the Makefile]

Hmm, xcodebuild on macOS fails with:

 ../../JuceLibraryCode/modules/juce_core/native/juce_osx_ObjCHelpers.h:225:95: error: use of undeclared identifier 'objc_msgSend_fpret'
static inline MsgSendFPRetFn getMsgSendFPRetFn() noexcept   { return (MsgSendFPRetFn) (void*) objc_msgSend_fpret; }
                                                                                              ^
1 error generated.

Any help with building FirmwareSender on macOS is appreciated.

Windows will be a whole other challenge ...

Found a juce7 fork of FirmwareSender and got CI to build a release for us: https://github.com/Wasted-Audio/FirmwareSender_plugdata/releases/tag/plugdata

Bit surprised that the Linux build is so much bigger, but maybe the macOS and Windows builds use a lot of system libs?
Will of course need testing to confirm everything works.

Linux works, but macOS gets stuck on connecting to the MIDI port with FirmwareSender:

CoreMIDI error: 1214 - ffffffce
MIDI device not avaialble: OWL-*
make: *** [Makefile:147: store] Error 255

Also: when manually downloading the toolchain all of the macOS binaries need to get their quarantine bit removed (should that be resolved on release?).

May need to try debug build for macOS as according to this bug report that might work: pingdynasty/FirmwareSender#4

[edit: confirmed that Debug build does work on macOS! - now we just need to test Windows]

Tested on Windows 11 and after some more tweaks it works!