package.sh: clean up FIFO properly (re: 936802f9)

Not cleaning up the FIFO broke 'grep -r' in the arch directory,
making it hang forever. So we need a better way of cleaning it up.

bin/package,
src/cmd/INIT/package.sh:
- Unlink the FIFO early after sleeping a second in the background.
  This works because the named directory entry is only needed to
  establish the pipe, not to keep it going.

bin/package

@@ -3973,6 +3973,11 @@ capture() # file command ...
 			# the main shell environment and its exit status can be used for $error_status
 			rm -f $o.fifo
 			mkfifo -m 600 $o.fifo || exit
+			(
+				sleep 1
+				# unlink early
+				exec rm $o.fifo
+			) &
 			$TEE -a $o < $o.fifo &
 			{
 				case $s in

src/cmd/INIT/package.sh

@@ -3972,6 +3972,11 @@ capture() # file command ...
 			# the main shell environment and its exit status can be used for $error_status
 			rm -f $o.fifo
 			mkfifo -m 600 $o.fifo || exit
+			(
+				sleep 1
+				# unlink early
+				exec rm $o.fifo
+			) &
 			$TEE -a $o < $o.fifo &
 			{
 				case $s in