Even if we don't see error messages from `llvm-dsymutil`, we can still
generate dSYM bundles that `dump_syms` completely falls over on. Let's
implement a super-careful check that actually examines the debug
information produced to ensure that `dump_syms` will accept our bundle.
Differential Revision: https://phabricator.services.mozilla.com/D44529
--HG--
extra : moz-landing-system : lando