OK.

The patch worked just fine.

Details:

Using Xcode-beta5:

git checkout emacs-26
gmake clean
cd src 
patch < ../path/to/your/path
cd ..
gmake install
cp -r nextstep/Emacs.app /Applications/

Hopefully that’s a reasonable path to rebuilding and running.

I then launched and can see all the rendered text just fine.

Also, switching to “Dark Mode” changes the window-title bar to the correct color.

Subjective, but scrolling seems faster, somehow.