[msandr] Add NATIVE_EXEC macro for building client for running in DynamoRIO hybrid mode only.

When running application in DynamoRIO hybrid mode only, only uninstrumented
modules will run in DynamoRIO and be instrumented by the client, so we do not
need module table in MSanDR.

Patch by Qin Zhao.



git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@193411 91177308-0d34-0410-b5e6-96231b3b80d8