packages: Convert world to a subdir build

Instead of driving the world package build from Makefile.inc1,
use a subdir build where each package has a subdirectory under
packages/ using the new <bsd.pkg.mk>.

Convert some metadata that was previously in the UCL files (e.g.
sets and dependencies) to Makefile variables.

Build the packages under objdir (not repodir), and use the new
stagepackages target to copy them to repodir when creating the
repository.

Determine an explicit list of packages to build in packages/Makefile
based on enabled src.conf options, and add logic to abort the build
if we attempt to build an empty package.  This inverts the previous
logic in Makefile.inc1 which would simply skip empty packages.

There are a few advantages to doing it this way:

* The package build works more like the rest of the build system,
  so it's more accessible to developers.

* We can customise the packages we build based on src.conf options,
  e.g. skipping a package entirely, or adjusting its dependencies
  based on what it actually requires.

* We have a specific list of packages that we want to build, and an
  unexpectedly missing package results in a build error, instead of
  silently producing a broken repository.

* It's possible to build (and in the future, install) an individual
  package without having to rebuild the entire repository.

This doesn't apply to the dtb, kernel-* or src-* packages; those
have their own build systems in Makefile.inc1 and will be converted
later.

MFC after:	4 weeks (stable/15 only)
Reviewed by:	jlduran, sjg, brooks
Sponsored by:	https://www.patreon.com/bsdivy
Differential Revision:	https://reviews.freebsd.org/D56087

1 files changed, 25 insertions, 0 deletions

diff --git a/packages/pkg-bootstrap/pkg-bootstrap.ucl b/packages/pkg-bootstrap/pkg-bootstrap.ucl
new file mode 100644
index 000000000000..493b1734e4a7
--- /dev/null
+++ b/packages/pkg-bootstrap/pkg-bootstrap.ucl
@@ -0,0 +1,25 @@
+/*
+ * SPDX-License-Identifier: ISC
+ *
+ * Copyright (c) 2025 Lexi Winter <ivy@FreeBSD.org>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+comment = "pkg(7) bootstrap utility"
+
+desc = <<EOD
+/usr/sbin/pkg is a minimal bootstrap tool used to install the full pkg(8)
+package management system.  This package also contains the public keys
+necessary to authenticate packages from the FreeBSD.org package repository.
+EOD