Windows make port works with MSYS shell

[Hiroshi Shirosaki]

Hello,

Now MSYS make with -jN (job server) hangs. This issue was reported at
the following list.
MSYS posix emulation(wait system call?) might not work fine.

http://comments.gmane.org/gmane.comp.gnu.mingw.user/40325


Windows port's job server works fine. I created a patch Windows port
to work fine with MSYS shell for build ruby.

https://gist.github.com/3888567#file_2_make_mingw_espace.patch

In my test, build of ruby, libyaml, tcl and tk works fine.


Changes:

* job.c: use shell with posix path command
If the command is like '/usr/bin/mkdir', shell is used always.

* w32/subproc/sub_proc.c:
Command line escape seems not to work well with CreateProcessW and
MSYS shell. So I changed the way to escape.

- Envirnment variables' double quotation escape changes
NAME="a b" => NAME=a\ b
NAME="" => NAME=

- Not quote arguments which have only head or trailing spaces


-- 
Hiroshi Shirosaki