Merge pull request #4101 from take-cheeze/fix_4085

Avoid root fiber initialization for CRuby.

minirake

@@ -6,12 +6,10 @@
 
 require 'getoptlong'
 require 'fileutils'
-require 'fiber'
 
 $rake_fiber_table = {}
 $rake_jobs = 1
 $rake_failed = []
-$rake_root_fiber = Fiber.current
 
 class String
   def ext(newext='')
@@ -111,10 +109,14 @@ module MiniRake
 
       if needed?
         @running = true
+        if $rake_root_fiber
           return Fiber.new do
             self.execute
             $rake_root_fiber.transfer
           end
+        else
+          self.execute
+        end
       end
 
       @done = true
@@ -308,7 +310,7 @@ module MiniRake
     def sh(cmd)
       puts cmd if $verbose
 
-      if $rake_jobs == 1 || Fiber.current == $rake_root_fiber
+      if !$rake_root_fiber || Fiber.current == $rake_root_fiber
         system(cmd) or fail "Command Failed: [#{cmd}]"
         return
       end
@@ -480,6 +482,12 @@ class RakeApp
   # Run the +rake+ application.
   def run
     handle_options
+
+    if $rake_root_fiber
+      require 'fiber'
+      $rake_root_fiber = Fiber.current
+    end
+
     begin
       here = Dir.pwd
       while ! have_rakefile
@@ -590,7 +598,7 @@ class RakeApp
     wait_process(count + 1) if !$rake_fiber_table.empty? && exited.empty?
   end
 
-  end
+end
 
 if __FILE__ == $0 then
   RakeApp.new.run