Add a check to all.gyp to respect the include_tests variable.

When include_tests==0, tests should be excluded from the build. This
ensures libjingle_tests.gyp is excluded appropriately.

BUG=b/15673188
R=tnakamura@webrtc.org, wu@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/16729005

git-svn-id: http://webrtc.googlecode.com/svn/trunk@6469 4adac7df-926f-26a2-2b94-8c16560cd09d

all.gyp

@@ -9,6 +9,7 @@
 {
   'variables': {
     'libjingle_root%': '<(DEPTH)',
+    'include_tests%': 1,
   },
   'targets': [
     {
@@ -19,7 +20,6 @@
         'webrtc/webrtc.gyp:*',
         '<(libjingle_root)/talk/libjingle.gyp:*',
         '<(libjingle_root)/talk/libjingle_examples.gyp:*',
-        '<(libjingle_root)/talk/libjingle_tests.gyp:*',
       ],
       'conditions': [
         ['OS=="android"', {
@@ -27,6 +27,11 @@
             'webrtc/webrtc_examples.gyp:*',
           ],
         }],
+        ['include_tests==1', {
+          'dependencies': [
+            '<(libjingle_root)/talk/libjingle_tests.gyp:*',
+          ],
+        }],
       ],
     },
   ],