Bug 724533 is going to probably semi-break standalone builds that come from a tarball that includes only mfbt/ and js/src. In the short run that's the right thing to do -- Intl stuff, and Norbert particularly, shouldn't get held up on packaging issues. In the long run, certainly no later than SpiderMonkey 24, standalone tarballs will obviously need to be fixed. I'm not sure if that means including intl/icu in the tarball or what, exactly. Embedder input is needed as to what's the best fix, after we get the Intl stuff all working. Obviously embedders are going to want something like --enable-system-icu=/path/to/icu as well. That might or might not be a separate bug, depending on what the ideal fix for standalone source tarball building is.

Mike Hommey suggested moving the ICU sources into js/src, which would make this easier. The --with-system-icu issue is tracked separately in bug 851992.

Mass-moving existing Intl-related bugs to the new Core :: JavaScript: Internationalization API component. If you think this bug has been moved in error, feel free to move it back to Core :: JavaScript Engine. [Mass change filter: core-js-intl-api-move]

Is this still a concern? Or can we close it now?

Pretty sure this is not a concern anymore, since the ICU sources are indeed included in generated SpiderMonkey standalone tarballs.