Add targets/pseudo/bootstrap-packages

Try to compensate for the lack any origin for a DIRDEPS build.

bootstrap-packages will extract the PACKAGE lines from
the tree's Makefiles and use them to populate
targets/packages/Makefile.depend and targets/packages/*/Makefile.depend
so we can at least try to keep the Makefile.depend files throughout
the tree up to date.

This is far from ideal, as we cannot (easily) take into account
options that affect the contents of various packages.

Reviewed by:	stevek
Sponsored by:	Juniper Networks, Inc.
Differential Revision:	https://reviews.freebsd.org/D47065

targets/pseudo/bootstrap-packages/Makefile

@@ -0,0 +1,23 @@
+# SPDX-License-Identifier: BSD-2-Clause
+#
+# Compensate (a bit) for the lack of per package makefiles or other means
+# of knowing what goes in each package in the base system.
+# We can derive some of the information we want from the makefiles that
+# set PACKAGE.
+
+all:
+.if ${.MAKE.LEVEL} > 0
+all: packages
+.endif
+
+PACKAGES?= ${.CURDIR:H:H}/packages
+
+packages: package-makefile.list
+	@${.CURDIR}/bootstrap-packages.sh PACKAGES=${PACKAGES} ${.ALLSRC}
+
+package-makefile.list:
+	@(cd ${SRCTOP} && \
+	find ${TOPS:U*bin etc lib*} -name 'Makefile' | \
+	xargs grep '^PACKAGE[[:space:]]*=' ) | \
+	sed 's/[[:space:]]*=[[:space:]]*/=/' > ${.TARGET}
+

targets/pseudo/bootstrap-packages/bootstrap-packages.sh

@@ -0,0 +1,96 @@
+#!/bin/sh
+
+# SPDX-License-Identifier: BSD-2-Clause
+
+# Our input is the output of something like:
+#
+#	(cd ${SRCTOP} &&
+#	find *bin etc lib* -name Makefile |
+#	xargs grep '^PACKAGE[[:space:]]*=' )
+#
+# With some cleanup and looks like:
+#
+#	usr.bin/ofed/libibverbs/Makefile:PACKAGE=FreeBSD-rdma
+#	usr.bin/last/Makefile:PACKAGE=acct
+#	usr.bin/lastcomm/Makefile:PACKAGE=acct
+#	usr.bin/users/Makefile:PACKAGE=acct
+#	usr.bin/who/Makefile:PACKAGE=acct
+#	usr.sbin/ac/Makefile:PACKAGE=acct
+#	usr.sbin/accton/Makefile:PACKAGE=acct
+#	usr.sbin/lastlogin/Makefile:PACKAGE=acct
+#	..
+#
+# which we use to populate $PACKAGES/*/Makefile.depend
+# and $PACKAGES/Makefile.depend to make it easier to keep
+# Makefile.depend files throughout the tree up-to-date.
+#
+# The result is not ideal, as we do not (yet) take into account all
+# the MK_* knobs that can impact DIRDEPS.
+#
+
+Mydir=`dirname $0`
+
+while :
+do
+    case "$1" in
+    *=*) eval "$1"; shift;;
+    *) break;;
+    esac
+done
+
+to_reldir() {
+    sed "s,$SRCTOP/,,"
+}
+
+SRCTOP=${SRCTOP:-$(realpath $Mydir/../../..)}
+PACKAGES=${PACKAGES:-$(realpath $Mydir/../..)}
+case "$PACKAGES" in
+/*) ;;
+*) PACKAGES=$SRCTOP/$PACKAGES;;
+esac
+
+script_name=$(realpath $0 | to_reldir)
+
+start_depend() {
+    depfile=$1
+
+    mkdir -p ${depfile%/*}
+    cat <<EOF > $depfile
+# Generated by $script_name
+
+DIRDEPS= \\
+EOF
+}
+
+end_depend() {
+    depfile=$1
+
+    cat <<EOF >> $depfile
+
+.include <dirdeps.mk>
+EOF
+}
+
+start_depend $PACKAGES/Makefile.depend || exit 1
+sort -t= -k2 "$@" | sed 's,/Makefile:PACKAGE=, ,' |
+(
+    lpackage=
+    while read reldir package
+    do
+        case "$package" in \
+	lib?{LIB}) package=${reldir##*/};;
+	lib?{LIB:tl}) package=`echo ${reldir##*/} | tr 'A-Z' 'a-z'`;;
+	esac
+	if test "$package" != "$lpackage"; then \
+	    test -z "$lpackage" || end_depend $ddeps
+	    target=$PACKAGES/$package
+            ddeps=$target/Makefile.depend
+            start_depend $ddeps
+	    lpackage=$package
+	    echo "	$target \\"
+	fi
+	echo "	$reldir \\" >> $ddeps
+    done
+    end_depend $ddeps
+) | to_reldir >> $PACKAGES/Makefile.depend
+end_depend $PACKAGES/Makefile.depend