p4c Update README.md instructions for running doxygen

Jul 15 '24 18:07 jafingerhut

@AdarshRawat1 These changes make sense to me regarding my confusions about running doxygen. Let me know if you see anything in these changes that is different than what you would recommend.

In particular, if we want to recommend using cmake with -DENABLE_DOCS=ON, it would be good to make those instructions work. Right now all of my attempts to use those steps have resulted in an error message, as mentioned in this issue: https://github.com/p4lang/p4c/issues/4805

Jul 15 '24 18:07 jafingerhut

@fruffy I am guessing the one failing test has nothing to do with changes to the README.md. I am leaving it there for now, in case you want to examine it and see if its root cause looks familiar to you. I do not know why it occurred.

Jul 15 '24 21:07 jafingerhut

Looks like a racecondition to me. Not quite clear why the Python lex/yacc code is sharing state here.

Jul 15 '24 21:07 fruffy

@AdarshRawat1 Could you please take a look at these changes and give any comments, or suggestions for further changes, that you think of?

Jul 18 '24 16:07 jafingerhut

@AdarshRawat1 Could you please take a look at these changes and give any comments, or suggestions for further changes, that you think of?

Since we only have a stable configuration for HTML output, these changes make total sense.

Jul 19 '24 10:07 AdarshRawat1