test_require.rb: reduce GC

* test/ruby/test_require.rb (test_loading_fifo_fd_leak): invoke GC
  only when FDs exhausted to reduce the test time.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@56462 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

test/ruby/test_require.rb

@@ -769,9 +769,13 @@ class TestRequire < Test::Unit::TestCase
         100.times do |i|
           Thread.start {begin sleep(0.001) end until th.stop?; th.raise(IOError)}
           assert_raise(IOError, "\#{i} time") do
-            tap {tap {tap {load(ARGV[0])}}}
+            begin
+              tap {tap {tap {load(ARGV[0])}}}
+            rescue LoadError
+              GC.start
+              retry
+            end
           end
-          GC.start
         end
       end;
     }