Fix Makefile to work on CentOS

```
Unfortunately, CentOS 5.8 has some stupid version of flex that does not 
tolerate a space after -o:

http://sourceware.org/ml/crossgcc/2012-06/msg00008.html

Please change:

  flex  -o moe/scrubber/comment.yy.c moe/scrubber/comment.l

to:

  flex  -omoe/scrubber/comment.yy.c moe/scrubber/comment.l
```

Original issue reported on code.google.com by `bolinf...@gmail.com` on 22 Mar 2013 at 7:09
