Parse enough of config.yaml to auto-generate config.auto.h and config.auto.c.
This commit implements most of the infrastructure needed to migrate the rest of the build code to C, but each set of auto-generated files will present its own challenges.
The build is now dependent on libyaml. At this point there is no need for a hard requirement, but that will come soon so it seems better to add the dependency now.
Both FreedBSD and MacOS use clang as their default compiler and clang catches some errors that gcc does not. Specifically, wide integers being assigned to short integers resulting in possible truncations.
Moving to YAML allows the configuration data to be read by C programs.
Also go back to using YAML::XS since it is the only implementation that has proper boolean support.
The archive-push command will continue to push even after it gets a write error on one or more repos. The idea is to archive to as many repos as possible even we still need to throw an error to PostgreSQL to prevent it from removing the WAL file.
Repositories will be searched in order for the requested archive file.
Errors will be reported as warnings as long as a valid copy of the archive file is found.
The unit test Makefile generation was a hodge-podge of constants and rules based on distros/versions that easily got out of date and did not work on an unknown system. All of this dates from the mixed Perl/C unit test implementation.
Instead use configure to generate most of the important Makefile variables, which allows the unit tests to run on multiple platforms, e.g. MacOS and FreeBSD.
There is plenty of work to be done here and not all the unit tests work on MacOS and FreeBSD for various reasons.
As a POC update the MacOS and FreeBSD tests on Cirrus-CI to run a few command unit tests.
Building on these platforms gives us better coverage for our build code. Cirrus CI was chosen because it is the only service that supports FreeBSD (that we could find).
The FreedBSD configuration for Vagrant is currently just enough to perform a build.
The MacOS configuration is not actually for Vagrant (yet) but does show the steps needed to setup the build environment on MacOS.
