Merging r360212:

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r360212 | kamil | 2019-05-07 17:44:41 -0700 (Tue, 07 May 2019) | 6 lines

Fix build on NetBSD 8.99.38

With recent changes the dev/nvmm/nvmm_ioctl.h header is no longer
a standalone NVMM header. Disable it until the NVMM operations will
stabilize and be included in the ioctl(2) interceptors.

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llvm-svn: 360811