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

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

Change-Id: I6daa2c4e847c7af52b3108326b9e13ccba4c662e