Merge r311269 into 5.0 branch: Use va_copy instead of __va_copy to fix building libomp against musl libc

[hahnjo]

Bugzilla Link	35168
Resolution	FIXED
Resolved on	Nov 14, 2017 11:17
Version	unspecified
OS	All
Blocks	#33840
CC	@AndreyChurbanov,@jpeyton52,@tstellar
Fixed by commit(s)	r311269 r318175

Extended Description

Fixes #33387

[hahnjo]

assigned to @AndreyChurbanov

[tstellar]

Hi Andrey,

Is this OK to merge to the release_50 branch: https://reviews.llvm.org/rL311269

[AndreyChurbanov]

Yes, it is OK to merge.

[tstellar]

Merged: r318175