Ruby

mjit.c: split build stages for unix

I'm going to build a large .so file that combines multiple .o files.
For that change, I want to confirm the impact to performance by this
change. So far, I haven't seen the significant change on the max
performance.

• before
  $ for i in 1 2 3 4 5 6 7 8 9 1 2; do ruby --jit ../../mame/optcarrot/bin/optcarrot --benchmark ../../mame/optcarrot/examples/Lan_Master.nes; done
  fps: 67.66058054621772
  checksum: 59662
  fps: 67.53138656233348
  checksum: 59662
  fps: 67.44109425628592
  checksum: 59662
  fps: 70.29423063961576
  checksum: 59662
  fps: 72.0147653358158
  checksum: 59662
  fps: 69.40157398157892
  checksum: 59662
  fps: 72.3984212467565
  checksum: 59662
  fps: 67.15473484463604
  checksum: 59662
  fps: 70.14142014098444
  checksum: 59662
  fps: 72.51761974327023
  checksum: 59662
  fps: 72.41086970333218
  checksum: 59662

• after
  $ for i in 1 2 3 4 5 6 7 8 9 1 2; do ruby --jit ../../mame/optcarrot/bin/optcarrot --benchmark ../../mame/optcarrot/examples/Lan_Master.nes; done
  fps: 69.53134628999938
  checksum: 59662
  fps: 66.13157649232654
  checksum: 59662
  fps: 70.17474368971281
  checksum: 59662
  fps: 61.88316323809907
  checksum: 59662
  fps: 72.48731307319704
  checksum: 59662
  fps: 65.1180687907147
  checksum: 59662
  fps: 68.89553415996615
  checksum: 59662
  fps: 65.77342314036225
  checksum: 59662
  fps: 64.33337015048106
  checksum: 59662
  fps: 64.98152672793444
  checksum: 59662
  fps: 72.225729092625
  checksum: 59662

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@64052 b2dd03c8-39d4-4d8f-98ff-823fe69b080e