benchmark/bm_vm2_fiber_switch.rb: check for fiber performance

There are currently no benchmarks for Fiber performance, I
should've committed this years ago when [Feature #10341] was
implemented.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@58606 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

benchmark/bm_vm2_fiber_switch.rb

@@ -0,0 +1,9 @@
+# based on benchmark for [ruby-core:65518] [Feature #10341] by Knut Franke
+fib = Fiber.new do
+  loop { Fiber.yield }
+end
+i = 0
+while i< 6_000_000 # benchmark loop 2
+  i += 1
+  fib.resume
+end