[Scons] Added the ability to change the visibility of symbols

(cherry picked from commit f5e4f95cde)

tools/godotcpp.py

@@ -291,6 +291,15 @@ def options(opts, env):
         )
     )
 
+    opts.Add(
+        EnumVariable(
+            key="symbols_visibility",
+            help="Symbols visibility on GNU platforms. Use 'auto' to apply the default value.",
+            default=env.get("symbols_visibility", "hidden"),
+            allowed_values=["auto", "visible", "hidden"],
+        )
+    )
+
     opts.Add(
         EnumVariable(
             "optimize",