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

Weak symbols are currently broken in upstream emscripten.

(cherry picked from commit 070bd87aaa)

platform/javascript/detect.py

@@ -201,6 +201,8 @@ def configure(env):
             sys.exit(255)
         env.Append(CCFLAGS=["-s", "RELOCATABLE=1"])
         env.Append(LINKFLAGS=["-s", "RELOCATABLE=1"])
+        # Weak symbols are broken upstream: https://github.com/emscripten-core/emscripten/issues/12819
+        env.Append(CPPDEFINES=["ZSTD_HAVE_WEAK_SYMBOLS=0"])
         env.extra_suffix = ".gdnative" + env.extra_suffix
 
     # Reduce code size by generating less support code (e.g. skip NodeJS support).