[Libguestfs] [PATCH nbdkit 5/9 patch split 1/5] Create libnbdkit.so.

[Richard W.M. Jones]

This is the previous 5/9 patch posted earlier today, split into
reviewable chunks.  This passes bisection with -x 'make && make
check', but I didn't work very hard on the commit messages, so I refer
you back to the original patch to explain how it works:

https://www.redhat.com/archives/libguestfs/2020-March/msg00248.html

Rich.