build/chroot: add small helper for this operation

Makefile

@@ -1,6 +1,6 @@
-STEPS=		base clean core distfiles kernel iso \
-		memstick nano plugins ports prefetch \
-		rebase regress release skim
+STEPS=		base chroot clean core distfiles kernel iso \
+		memstick nano plugins ports prefetch rebase \
+		regress release skim
 .PHONY:		${STEPS}
 
 PAGER?=		less

README.md

@@ -196,3 +196,8 @@ In case a release was wrapped up, the base package list and obsoleted
 files need to be regenerated.  This is done using:
 
     # make rebase
+
+Shall any debugging be needed inside the build jail, the following
+command will use chroot(8) to enter the active build jail:
+
+    # make chroot

build/chroot.sh

@@ -0,0 +1,34 @@
+#!/bin/sh
+
+# Copyright (c) 2016 Franco Fichtner <franco@opnsense.org>
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions
+# are met:
+#
+# 1. Redistributions of source code must retain the above copyright
+#    notice, this list of conditions and the following disclaimer.
+#
+# 2. Redistributions in binary form must reproduce the above copyright
+#    notice, this list of conditions and the following disclaimer in the
+#    documentation and/or other materials provided with the distribution.
+#
+# THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+# ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+# SUCH DAMAGE.
+
+set -e
+
+. ./common.sh && $(${SCRUB_ARGS})
+
+echo ">>> chroot'ing into ${STAGEDIR}..."
+
+chroot ${STAGEDIR} /bin/csh