Add linux/userfaultfd.h header file to host glibc am: 9993489d1c am: e49b4b3477 am: 007101a451

Original change: https://android-review.googlesource.com/c/platform/prebuilts/gcc/linux-x86/host/x86_64-linux-glibc2.17-4.8/+/1999534

Change-Id: I7d3e0430338e3022cdf9739838565c5b0e674839