Also update BUILD.gn to include 2 new headers under `msinttypes/`.
Do not include the bin/ directory which contains bad characters that the
presbumit catches.

TEST=Built fuchsia with ubsan and runtests, and run GI tests

Bug: 39857
Change-Id: Id5dd7288af79e042d4c2efd6ed5ead411a08f4b6