Add Objective-C bridging tests for NSString, NSArray, NSDictionary, NSSet

The tests test conditional and forced bridging from objective-c and bridging to
objective-c.

Author: aschwaighofer

benchmark/CMakeLists.txt

@@ -59,6 +59,7 @@ set(SWIFT_BENCH_MODULES
     single-source/NSError
     single-source/NSStringConversion
     single-source/ObjectAllocation
+    single-source/ObjectiveCBridging
     single-source/OpenClose
     single-source/Phonebook
     single-source/PolymorphicCalls