[Windows/MinGW] Only export extension init symbol

When building for Windows using MinGW GCC we need to apply the same
workaround we use on Linux to only export the necessary symbols so we
can safely statically link libstdc++

SConstruct

@@ -167,11 +167,13 @@ env.Depends(sources, ssl + rtc)
 # symbols using a GCC version script, or we might end up overriding symbols from other libraries.
 # Using "-fvisibility=hidden" will not work, since libstdc++ explicitly exports its symbols.
 symbols_file = None
-if env["platform"] == "linux":
+if env["platform"] == "linux" or (
+    env["platform"] == "windows" and env.get("use_mingw", False) and not env.get("use_llvm", False)
+):
     if env["godot_version"] == "3":
-        symbols_file = env.File("misc/dist/linux/symbols-gdnative.map")
+        symbols_file = env.File("misc/gcc/symbols-gdnative.map")
     else:
-        symbols_file = env.File("misc/dist/linux/symbols-extension.map")
+        symbols_file = env.File("misc/gcc/symbols-extension.map")
     env.Append(
         LINKFLAGS=[
             "-Wl,--no-undefined,--version-script=" + symbols_file.abspath,