default.mspec: job server

* spec/default.mspec: override MSpecScript#cores by the tokens
  from the parent make job server.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@58251 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

spec/default.mspec

@@ -24,3 +24,28 @@ class MSpecScript
     --
   ]
 end
+
+class MSpecScript
+  if /(?:\A|\s)--jobserver-(?:auth|fds)=(\d+),(\d+)/ =~ ENV["MAKEFLAGS"]
+    begin
+      r = IO.for_fd($1.to_i(10), "rb", autoclose: false)
+      w = IO.for_fd($2.to_i(10), "wb", autoclose: false)
+    rescue
+      r.close if r
+    else
+      jobtokens = r.read_nonblock(1024)
+      cores = jobtokens.size
+      if cores > 0
+        jobserver = w
+        at_exit {
+          jobserver.print(jobtokens)
+          jobserver.close
+        }
+      end
+      remove_method :cores
+      define_method(:cores) do
+        cores
+      end
+    end
+  end
+end