It turns out the simple s/simplejson/json/ didn't work because
build_tooltool_manifest used item_sort_key to ensure that the objects
read in were written out in the same order. This scheme was brittle,
since it only understand a couple of keys from the manifest file, and it
doesn't work with the stdlib json.
Instead, use object_pairs_hook=collections.OrderedDict with json.load,
which ensures that current objects get written out in the same order
they were read in *and* that any future keys will be handled
automagically.
DONTBUILD because NPOTB
a83b0a8ab2