Merging r341442:
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r341442 | bcain | 2018-09-05 04:15:54 +0200 (Wed, 05 Sep 2018) | 8 lines

Add glibc_prereq to platform limits mmsghdr

sendmmsg requires glibc >= 2.14.

Fixes PR38589.

Review: https://reviews.llvm.org/D51538

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git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/branches/release_70@341524 91177308-0d34-0410-b5e6-96231b3b80d8