Fix unintentional revert of SYMROOT change to testing/iossim.

A change made to iossim.gyp in https://chromiumcodereview.appspot.com/14835006
was unintentionally reverted by https://chromiumcodereview.appspot.com/14597007.

Restoring CL 14835006 updates the iossim output path to use $(SYMROOT).

BUG=None
TEST=None

Review URL: https://chromiumcodereview.appspot.com/19985004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@213010 0039d316-1c4b-4281-b951-d872f2087c98

diff --git a/testing/iossim/iossim.gyp b/testing/iossim/iossim.gyp
index a5c9d30a..b699b53 100644
--- a/testing/iossim/iossim.gyp
+++ b/testing/iossim/iossim.gyp

@@ -55,7 +55,7 @@
       'variables': {
         'ninja_output_dir': 'ninja-iossim',
         'ninja_product_dir':
-          '<(DEPTH)/xcodebuild/<(ninja_output_dir)/<(CONFIGURATION_NAME)',
+          '$(SYMROOT)/<(ninja_output_dir)/<(CONFIGURATION_NAME)',
       },
       'targets': [
         {