Remove <linux/prctl.h> from backend.c via Build/Prepare sed: both
<linux/prctl.h> and <sys/prctl.h> define struct prctl_mm_map in newer
musl toolchains, causing a redefinition build error. sys/prctl.h alone
provides everything fio needs.
Changelog: https://github.com/axboe/fio/blob/fio-3.42/HOWTO.rst
Signed-off-by: Alexandru Ardelean <alex@shruggie.ro>