extconf-c.rb.tt in rubygems-update-3.4.11

- old
+ new

@@ -1,5 +1,10 @@
 # frozen_string_literal: true
 
 require "mkmf"
 
+# Makes all symbols private by default to avoid unintended conflict
+# with other gems. To explicitly export symbols you can use RUBY_FUNC_EXPORTED
+# selectively, or entirely remove this flag.
+append_cflags("-fvisibility=hidden")
+
 create_makefile(<%= config[:makefile_path].inspect %>)