Fix broken pipe caused by commands in toolchain.gypi.

Fix broken pipe caused by commands in toolchain.gypi.

I sometimes observe broken pipe errors when I run gyp, which causes the gyp
process to fail. This seems to happen if gyp is executed under heavy I/O
pressure.

This change removes the pipes by replacing "echo |" with "< /dev/null".
Technically these are not the same, because "echo |" prints a newline while
"< /dev/null" doesn't, but this difference is not significant in the context of
the commands in toolchain.gypi.

BUG=
R=jkummerow@chromium.org

Committed: http://code.google.com/p/v8/source/detail?r=17836

[Yuta Kitamura, 2013-11-15 04:02:11]

Hi jkummerow, could you review this?

I'm not a committer in V8, so if you could land this
after the review, that's much appreciated!

(It's first time for me to upload a patch for V8, so I
 apologize if I did something wrong in the review process.)

[Jakob Kummerow, 2013-11-18 14:30:55]

LGTM.

FWIW, I've never seens those pipes break, but if this helps... fine.

[Jakob Kummerow, 2013-11-18 14:32:36]

Committed patchset #1 manually as r17836 (presubmit successful).