This reverts commit 2cd20c255684257b86940bdda6861897f0bf3c00.
This relands commit 9886788a8a500a1b429a6db64397c849b112251c.
This was causing more buildbot failures due to getcpu not being
available with glibc <=2.29. This patch fixes that by directly making
the syscall, assuming the syscall number macro is available.