Those tests currently only work when a single table is the target of the
load, and when this target is explicit in the INTO target clause. More
work needs to be done to cover interesting cases like MySQL and SQLite
where we want to diff a full database rather than a single table.
Including some Makefile hacks where test doesn't depend on the main pgloader
binary anymore because I coulnd't stop the binary to get being built again
even if it's been done already...