Merging r369364:

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r369364 | miyuki | 2019-08-20 12:19:55 +0200 (Tue, 20 Aug 2019) | 6 lines

[libcxx] Fix build breakage on mips

Fixes https://bugs.llvm.org/show_bug.cgi?id=43011 caused by
https://reviews.llvm.org/D63284.

Committing as obvious.
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llvm-svn: 369898