Merging r354765:

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r354765 | kadircet | 2019-02-25 10:19:26 +0100 (Mon, 25 Feb 2019) | 9 lines

[clangd] Add thread priority lowering for MacOS as well

Reviewers: ilya-biryukov

Subscribers: ioeric, MaskRay, jkorous, arphaman, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D58492
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llvm-svn: 354983