runc: depend on linux headers >= 3.11 for O_TMPFILE

Fixes:
http://autobuild.buildroot.net/results/63e9d88ae5177541be463f1e2aafec59aa410479



Add dependency on headers >= 3.11 for O_TMPFILE, used by runc after the
fix for CVE-2019-5736 and propagate to the reverse dependencies of runc.

Notice that C library support for O_TMPFILE is also needed, which was added
in glibc 2.19 and musl 0.9.15.

Signed-off-by: Christian Stewart <christian@paral.in>
[Peter: squash series, extend commit message, mention C library dependency,
	fix indentation]
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>