As noted in #2265 and #2352 , the Readme still has some redundant and somewhat outdated/out of sync information versus what is currently in the build docs (doc/build) and the build.py script, including detailed description of setting up, building and viewing the docs with Sphinx that is now covered in updated form in doc/build.rst, and listing the build.py options, which are now in the script --help, and are redundant and will drift out of sync here, and which we removed from build.rst for that reason. Therefore, for each, we refer the reader to the respective canonical sources for this information, while leaving a concise high-level summary remaining in the Readme.