How to build a static Unison binary

The current documentation for Unison (as at 2.32.52) is slightly out of date, because the STATIC=true option to the Makefile does not do anything. The fix is to grab the patch file from this post and then apply it as follows:

cd unison-2.32.52
patch -p0 < ../patch-unison-static
make STATIC=true

Very handy if you have to run unison on a system with an old glibc.