Restore -rdynamic in Product mode build

runtime/bin/BUILD.gn

Index: runtime/bin/BUILD.gn
diff --git a/runtime/bin/BUILD.gn b/runtime/bin/BUILD.gn
index 8de7a1b0a8c302a9ddad2128b315cade52c1130c..4d9ec19a196de318b672cdd215dbfe53b6bbe6a4 100644
--- a/runtime/bin/BUILD.gn
+++ b/runtime/bin/BUILD.gn
@@ -660,9 +660,9 @@ template("dart_executable") {
     if (is_win) {
       ldflags = [ "/EXPORT:Dart_True" ]
     } else {
-      if (dart_runtime_mode != "release") {
-        ldflags = [ "-rdynamic" ]
-      }
+      # Adds all symbols to the dynamic symbol table, not just used ones.
+      # This is needed to make native extensions work.
+      ldflags = [ "-rdynamic" ]
     }
 
     if (is_win) {