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Pass required flags "-rpath @executable/Frameworks" when linking
executable to point to the location where the custom frameworks
are located in iOS builds.

Pass flags "-objc_abi_version 2" to linker flag for execuable and
dynamic libraries as is done by Xcode and remove one intermediate
config object (unnecessary).

BUG=None

Review-Url: https://codereview.chromium.org/2326543003
Cr-Commit-Position: refs/heads/master@{#417403}