Merging r352806:

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r352806 | sbc | 2019-01-31 14:38:22 -0800 (Thu, 31 Jan 2019) | 5 lines

[WebAssembly] MC: Fix for outputing wasm object to /dev/null

Subscribers: dschuff, jgravelle-google, aheejin, sunfish, llvm-commits

Differential Revision: https://reviews.llvm.org/D57479
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llvm-svn: 360949