Index: tools/build/depend-cleanup.sh
===================================================================
--- tools/build/depend-cleanup.sh
+++ tools/build/depend-cleanup.sh
@@ -17,12 +17,65 @@
 # anyone would try a NO_CLEAN build against an object tree from before the
 # related change.  One year should be sufficient.
 
+set -e
+set -u
+
+warn()
+{
+	echo "$(basename "$0"):" "$@" >&2
+}
+
+err()
+{
+	warn "$@"
+	exit 1
+}
+
+usage()
+{
+	echo "usage: $(basename $0) [-v] [-n] objtop" >&2
+}
+
+VERBOSE=
+PRETEND=
+while getopts vn o; do
+	case "$o" in
+	v)
+		VERBOSE=1
+		;;
+	n)
+		PRETEND=1
+		;;
+	*)
+		usage
+		exit 1
+		;;
+	esac
+done
+shift $((OPTIND-1))
+
+if [ $# -ne 1 ]; then
+	usage
+	exit 1
+fi
+
 OBJTOP=$1
+shift
 if [ ! -d "$OBJTOP" ]; then
-	echo "usage: $(basename $0) objtop" >&2
+	err "$OBJTOP: Not a directory"
 	exit 1
 fi
 
+run()
+{
+	if [ "$VERBOSE" ]; then
+		echo "$@"
+	fi
+	if ! [ "$PRETEND" ]; then
+		"$@"
+	fi
+}
+
 # $1 directory
 # $2 source filename w/o extension
 # $3 source extension
@@ -31,7 +84,7 @@
 	if [ -e "$OBJTOP"/$1/.depend.$2.pico ] && \
 	    egrep -qw "$2\.$3" "$OBJTOP"/$1/.depend.$2.pico; then \
 		echo "Removing stale dependencies for $2.$3"; \
-		rm -f "$OBJTOP"/$1/.depend.$2.* \
+		run rm -f "$OBJTOP"/$1/.depend.$2.* \
 		    "$OBJTOP"/obj-lib32/$1/.depend.$2.*
 	fi
 }
@@ -47,14 +100,14 @@
     egrep -qw "cddl/contrib/opensolaris/lib/libzfs/common/libzfs_changelist.c" \
     "$OBJTOP"/cddl/lib/libzfs/.depend.libzfs_changelist.o; then
 	echo "Removing old ZFS tree"
-	rm -rf "$OBJTOP"/cddl "$OBJTOP"/obj-lib32/cddl
+	run rm -rf "$OBJTOP"/cddl "$OBJTOP"/obj-lib32/cddl
 fi
 
 # 20200916  WARNS bumped, need bootstrapped crunchgen stubs
 if [ -e "$OBJTOP"/rescue/rescue/rescue.c ] && \
     ! grep -q 'crunched_stub_t' "$OBJTOP"/rescue/rescue/rescue.c; then
 	echo "Removing old rescue(8) tree"
-	rm -rf "$OBJTOP"/rescue/rescue
+	run rm -rf "$OBJTOP"/rescue/rescue
 fi
 
 # 20210105  fda7daf06301   pfctl gained its own version of pf_ruleset.c
@@ -62,13 +115,13 @@
     egrep -qw "sys/netpfil/pf/pf_ruleset.c" \
     "$OBJTOP"/sbin/pfctl/.depend.pf_ruleset.o; then
 	echo "Removing old pf_ruleset dependecy file"
-	rm -rf "$OBJTOP"/sbin/pfctl/.depend.pf_ruleset.o
+	run rm -rf "$OBJTOP"/sbin/pfctl/.depend.pf_ruleset.o
 fi
 
 # 20210108  821aa63a0940   non-widechar version of ncurses removed
 if [ -e "$OBJTOP"/lib/ncurses/ncursesw ]; then
 	echo "Removing stale ncurses objects"
-	rm -rf "$OBJTOP"/lib/ncurses "$OBJTOP"/obj-lib32/lib/ncurses
+	run rm -rf "$OBJTOP"/lib/ncurses "$OBJTOP"/obj-lib32/lib/ncurses
 fi
 
 # 20210608  f20893853e8e    move from atomic.S to atomic.c