[ruby/fiddle] support for very old libffi

Define `Fiddle::TYPE_VARIADIC` only when `ffi_prep_cif_var` is
available, otherwise skip the test for it.

1 files changed, 3 insertions, 0 deletions

diff --git a/test/fiddle/test_func.rb b/test/fiddle/test_func.rb
index cf71a4b123..29a0a455f1 100644
--- a/test/fiddle/test_func.rb
+++ b/test/fiddle/test_func.rb
@@ -81,6 +81,9 @@ module Fiddle
     end
 
     def test_snprintf
+      unless Fiddle.const_defined?("TYPE_VARIADIC")
+        skip "libffi doesn't support variadic arguments"
+      end
       if Fiddle::WINDOWS
         snprintf_name = "_snprintf"
       else