this has regressed once more in swift 5.10, as we are no longer able to dump the symbol graphs for the Foundation or _StringProcessing modules with -emit-extension-block-symbols enabled.
i wish to underscore that fixing this cannot be deferred until after the 5.10 release, as the compiler currently does not have the ability to generate the symbol graph for any version of swift other than its own. therefore, if swift 5.10 ships with a broken symbol graph generator, it will never be possible to generate documentation (that includes cross-module extensions) for the 5.10 standard library, or packages that link against the 5.10 standard library.
