Maybe I'm missing something obvious, but I get an error with this change (on most-recent master):

$ git submodule update --init --recursive
fatal: reference is not a tree: 7edfb509c478c6c33a50369dcc8cf1485ac9fa69
Unable to checkout '7edfb509c478c6c33a50369dcc8cf1485ac9fa69' in submodule path 'external_libraries/hidapi'

@bagong gave me a hint recently that solved the problem: http://new-supercollider-mailing-lists-forums-use-these.2681727.n2.nabble.com/supercollider-supercollider-2f6d89-Update-pointer-to-hidapi-submodule-2330-tp7627745p7627748.html

Aha! git submodule sync fixed it -- I think the issue was my repo was still pointed at marije's fork and git submodule update --init --recursive didn't fix that for some reason.