DSO: reduce visibility of bdz lib

build.zig

@@ -59,6 +59,7 @@ pub fn build(b: *zbs.Builder) void {
     }, &.{
         "-W",
         "-Wno-unused-function",
+        "-fvisibility=hidden",
         //"-DDEBUG",
     });
     bdz.omit_frame_pointer = true;