[bitcode] Pass -bitcode_bundle to the linker when linking via swiftc.

...and either -embed-bitcode or -embed-bitcode-marker is passed. This is
the same behavior as Clang.

rdar://problem/20246442

Swift SVN r29387

lib/Driver/Tools.cpp

@@ -715,6 +715,11 @@ Job *darwin::Linker::constructJob(const JobAction &JA,
     Arguments.push_back("-application_extension");
   }
 
+  if (Args.hasArg(options::OPT_embed_bitcode,
+                  options::OPT_embed_bitcode_marker)) {
+    Arguments.push_back("-bitcode_bundle");
+  }
+
   if (!OI.SDKPath.empty()) {
     Arguments.push_back("-syslibroot");
     Arguments.push_back(Args.MakeArgString(OI.SDKPath));