Merging r247461:

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r247461 | Yunzhong_Gao | 2015-09-11 16:01:53 -0400 (Fri, 11 Sep 2015) | 4 lines

Add a non-exiting diagnostic handler for LTO.
This is in order to give LTO clients a chance to do some clean-up before
terminating the process.

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llvm-svn: 252774