[JS] Add flag to disable weak symbols in ZSTD.
[JS] Add flag to disable weak symbols in ZSTD.

Weak symbols are currently broken in upstream emscripten.

(cherry picked from commit 070bd87aaaf7a15ad9d2d839182f14d5c352153b)

ex/godot,ex/godot,ex/godot,ex/godot,ex/godot,ex/godot,ex/godot,ex/godot