[Cronet] Use developer_dir to find Xcode toolchain on official bots.

Bug: 774814
Cq-Include-Trybots: master.tryserver.chromium.android:android_cronet_tester;master.tryserver.chromium.mac:ios-simulator-cronet
Change-Id: I442f55b957017119b5241993ee0f90ae63a86557
Reviewed-on: https://chromium-review.googlesource.com/729126
Reviewed-by: Andrei Kapishnikov <[email protected]>
Commit-Queue: Misha Efimov <[email protected]>
Cr-Original-Commit-Position: refs/heads/master@{#510231}(cherry picked from commit d5ccb43)
Reviewed-on: https://chromium-review.googlesource.com/729380
Cr-Commit-Position: refs/branch-heads/3239@{#94}
Cr-Branched-From: adb61db-refs/heads/master@{#508578}

Author: Misha Efimov

components/cronet/tools/hide_symbols.py

@@ -60,14 +60,15 @@ def main():
 
   if options.developer_dir:
     os.environ['DEVELOPER_DIR'] = options.developer_dir
-    developer_dir = options.developer_dir
+    developer_dir = options.developer_dir + '/Contents/Developer'
   else:
     developer_dir = subprocess.check_output(
         ['xcode-select', '--print-path']).strip()
 
   xctoolchain_libs = glob.glob(developer_dir
       + '/Toolchains/XcodeDefault.xctoolchain/usr/lib'
       + '/clang/*/lib/darwin/*.ios.a')
+  print "Adding xctoolchain_libs: ", xctoolchain_libs
 
   # ld -r concatenates multiple .o files and .a files into a single .o file,
   # while "hiding" symbols not marked as visible.