ifdef out ProcessUtilTest.CloneFlags on linux with old kernel headers

ifdef out ProcessUtilTest.CloneFlags on linux with old kernel headers

This allows the rest of base_unittests to build/run on such
systems.

BUG=312380
Committed: https://crrev.com/3cf743a247fbd50936c0eaf395c2b1345813661b
Cr-Commit-Position: refs/heads/master@{#335123}

[Mostyn Bramley-Moore, 2015-06-18 10:19:45]

mostynb@opera.com changed reviewers:
+ rickyz@chromium.org, thestig@chromium.org

[Mostyn Bramley-Moore, 2015-06-18 10:21:35]

@Lei Zhang, rickyz: please take a look at this tiny fixup for linux targets with
old kernels/kernel headers.

[Lei Zhang, 2015-06-18 18:42:33]

3.8 is relatively new. Let's do this and revisit it in a couple years.

[rickyz (no longer on Chrome), 2015-06-18 19:28:00]

On 2015/06/18 18:42:33, Lei Zhang wrote:
> 3.8 is relatively new. Let's do this and revisit it in a couple years.

lgtm, thanks!

[Lei Zhang, 2015-06-18 20:35:11]

The CQ bit was checked by thestig@chromium.org

[Lei Zhang, 2015-06-18 20:35:12]

lgtm

[commit-bot: I haz the power, 2015-06-18 20:37:11]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1189683004/1

[commit-bot: I haz the power, 2015-06-18 21:13:00]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-06-18 21:14:00]

Patchset 1 (id:??) landed as
https://crrev.com/3cf743a247fbd50936c0eaf395c2b1345813661b
Cr-Commit-Position: refs/heads/master@{#335123}