Despite some files being under `third_party`, it's our files, that we can
modify.
We want to include codec headers using `<>` and not `""` because angle bracket
includes from `dist/system_wrappers` and not `dist/include`. The former location
wraps the include in a way that makes the symbols have a default visibility,
while the latter hides the symbol. Because those codecs have been moved to a
different shared library, we need their symbols exported.
Differential Revision: https://phabricator.services.mozilla.com/D176158