An obscure problem with v2.37 make check

[Bruce Dubbs <bruce.dubbs@gmail.com>]

When I built version v2.37, make check hung on me.  The problem was in 
my kernel configuration, but I thought I would pass this on.

First of all, my biggest problem was finding out what had failed.  A 
simple 'make check' ran the tests and when it got to the end, hung.

I could not find any documentation about running the tests, but diving 
into the Makefile led me to tests/run.sh.  By default this runs tests 
using all cores, but it is unclear if this is meant to be run directly.

In any case running run.sh --parallel=1 (instead of the default 24) 
allowed me to find the problem test, tests/ts/lsns/ioctl_ns.  In this 
test, it is doing:

my_userns=$(stat -c %i -L /proc/self/ns/user)

My problem was that /proc/self/ns/user did not exist on my system.  This 
was due to a missing CONFIG option in my kernel configuration.  Adding 
that and rebuilding the kernel allowed all tests to pass.

One solution to this problem may be to test for the existence of the 
file before running 'stat' similar to the tests for programs like 
'touch' and 'uniq'.  Since this is such an unusual situation, I can 
understand if you just ignore the issue, however I thought you should 
know about it.

   -- Bruce