Move -lrt where it belongs.

Only deqp uses librt so the dependency belongs there, not in util.gyp,
and the condition should be OS==linux, not use_x11.
This lets things work on Chrome OS.

BUG=angleproject:1297

Change-Id: If397da5463b9c2d5217eb3b20841fa5a44bf56a3
Reviewed-on: https://chromium-review.googlesource.com/334813
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Commit-Queue: Frank Henigman <fjhenigman@chromium.org>

src/tests/deqp.gypi

@@ -1380,6 +1380,13 @@
                         {
                             'sources': [ '<@(deqp_libtester_sources_unix)', ],
                         }],
+                        ['OS=="linux"',
+                        {
+                            'link_settings':
+                            {
+                                'libraries': ['-lrt']
+                            },
+                        }],
                     ],
                 },
 

util/util.gyp

@@ -158,7 +158,7 @@
                         ],
                         'libraries':
                         [
-                            '<!@(<(pkg-config) --libs-only-l x11 xi) -lrt',
+                            '<!@(<(pkg-config) --libs-only-l x11 xi)',
                         ],
                     },
                 }],