qemu-user-static: pull in fixes for the 2.x branch

Short list:

• __sysctlbyname(2) implemented
• posix_spawn breakage due to RFSPAWN averted
• some _umtx_op misbehavior fixed*

Some _umtx_op operations were processing a timeout, but failed to pass in
the size of the timespec/_umtx_time to the kernel, passing in '0' instead.
This would cause unbounded sleep until interrupted, rather than timeout
expected by the caller.

PR: 240763
Approved by: ler (ports), sbruno (maintainer, implicit)
MFH: 2019Q4 (runtime fix)