Fluxengine build on macOS 15.7.7

[RobertDaleMohr]

I am trying to get the flux engine command line tools built. I installed the prerequisites indicated on this page: http://cowlark.com/fluxengine/doc/building-client.html. After running make I get the following:

bash-3.2$ gmake
AB
loading build.py
loading build/c.py
loading build/utils.py
loading build/toolchain.py
loading build/protobuf.py
loading build/pkg.py
loading config.py
fluxengine-testdata not found; skipping corpus tests
package 'protobuf' found
package 'zlib' found
loading dep/fmt/build.py
package 'fmt' found
package 'sqlite3' found
loading src/build.py
loading dep/adflib/build.py
loading dep/agg/build.py
loading dep/alphanum/build.py
loading dep/fatfs/build.py
loading dep/hfsutils/build.py
loading dep/libusbp/build.py
loading dep/stb/build.py
loading lib/config/build.py
loading lib/core/build.py
loading lib/external/build.py
loading lib/decoders/build.py
loading arch/build.py
loading lib/fluxsink/build.py
loading lib/encoders/build.py
loading lib/fluxsource/build.py
loading lib/imagereader/build.py
loading lib/imagewriter/build.py
loading lib/usb/build.py
loading lib/vfs/build.py
loading lib/data/build.py
loading dep/lexy/build.py
loading lib/algorithms/build.py
loading src/formats/build.py
loading scripts/build.py
loading tests/build.py
loading src/gui2/build.py
Error materialising Target('+all'): <function export at 0x100cf1c70>
Arguments: {'self': Target('+all'), 'name': '+all'}
Traceback (most recent call last):
File "/Users/Faith/Downloads/fluxengine/build/ab.py", line 779, in
main()
~~~~^^
File "/Users/Faith/Downloads/fluxengine/build/ab.py", line 763, in main
t.materialise()
~~~~~~~~~~~~~^^
File "/Users/Faith/Downloads/fluxengine/build/ab.py", line 360, in materialise
raise e
File "/Users/Faith/Downloads/fluxengine/build/ab.py", line 324, in materialise
v = t.convert(v, self)
File "/Users/Faith/Downloads/fluxengine/build/ab.py", line 468, in convert
output = {k: target.targetof(v) for k, v in value.items()}
~~~~~~~~~~~~~~~^^^
File "/Users/Faith/Downloads/fluxengine/build/ab.py", line 379, in targetof
return targetof(value, self.cwd)
File "/Users/Faith/Downloads/fluxengine/build/ab.py", line 441, in targetof
loadbuildfile(path)
~~~~~~~~~~~~~^^^^^^
File "/Users/Faith/Downloads/fluxengine/build/ab.py", line 495, in loadbuildfile
spec.loader.exec_module(module)
~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^
File "/Users/Faith/Downloads/fluxengine/build/ab.py", line 98, in exec_module
super(SourceFileLoader, self).exec_module(module)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^
File "", line 759, in exec_module
File "", line 491, in _call_with_frames_removed
File "src/gui2/build.py", line 53, in
hdrs=headers_from("dep/nlohmann_json/single_include"),
~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "src/gui2/build.py", line 31, in headers_from
assert hdrs, f"path {path} contained no headers"
^^^^
AssertionError: path dep/nlohmann_json/single_include contained no headers
build/ab.mk:122: .obj/osx/build.targets: No such file or directory
gmake: *** [build/ab.mk:116: .obj/osx/build.targets] Error 1
bash-3.2$

Any advice?