Failing to build on osx.

## Description

I followed the build instructions, but when I tried to build on osx I get the following error.

>[ 9%] Built target libCZI
make[2]: *** No rule to make target `_deps/cel-spec-build/_gen_upb/proto/cel/expr/checked.upb.h', needed by `renderlib/CMakeFiles/renderlib_autogen_timestamp_deps'. Stop.

## Reproduction

I followed the instructions, except I already have qt6, I think this error is not related to Qt6. I tried both

git submodule update --init
git submodule sync

## Environment

OSX 26.5 with Qt 6.11.1 building from main