Linux: add an option to use system jsoncpp

Linux: add an option to use system jsoncpp

BUG=none

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=174979

[Ronghua Wu (Left Chromium), 2013-01-02 22:54:47]

In which case this option will be used?

And it seems only work for linux, you may want to add a condition for that.

[Paweł Hajdan Jr., 2013-01-02 23:03:01]

On 2013/01/02 22:54:47, Ronghua Wu wrote:
> In which case this option will be used?

This will be used by Linux distributions, and never for Google Chrome.

> And it seems only work for linux, you may want to add a condition for that.

This follows the general convention for this type of flag.

Please take a look at
http://www.chromium.org/developers/adding-3rd-party-libraries for more info.

[Ronghua Wu (Left Chromium), 2013-01-02 23:11:14]

Got it, thanks.

LGTM