Xcode 11.6 build time is very slow

I'm having the same problem with Xcode 11.3.

I finally got my project built without errors or warnings. I made a copy of the project directory, and my attempt to build the copied project seems to be hanging while displaying the "Using build description from memory" message. Previous copies of earlier stages, as I was eliminating errors, had no such problems, a copy would build with the same set of errors and warnings as the original project.

The fact that it's saying "from memory" concerns me. I've tried stopping Xcode and restarting it. I'm wondering if it might take rebooting to clear this "memory" issue. That's a pain to do, with all the stuff I have open, but if I don't find another solution, I'll try it. I'll try to report back here if I have any success.

I found numerous other complaints about the same issue and the apparently related issue that when starting Xcode, it would begin to index the text and never finish. Several users reported that restarting their system cleared up the problem <https://stackoverflow.com/questions/50015033/indexing-text-on-xcode>, so I tried it and it worked for me.