package: don't exit prematurely (re: 3e140727, 936802f9, d18469d6)

Sometimes the shell returned to the prompt before bin/package was
finished writing all of its output. The problem was that 'tee',
which is used to write the output to both the terminal and the log
in arch/*lib/package/gen/make.out, hadn't caught up yet.

bin/package, src/cmd/INIT/package.sh:
- Run the build itself in the background and 'tee' in the
  foreground. This way, the script will not terminate until 'tee'
  is finished. The build's exit status is obtained with 'wait'.

bin/package

@@ -4008,8 +4008,8 @@ capture() # file command ...
 		0)	if	executable ! $TEE
 			then	TEE=tee
 			fi
-			# Connect 'tee' to a FIFO instead of a pipe, so that the build is invoked from
+			# Connect 'tee' to a FIFO instead of a pipe, so that we can obtain
-			# the main shell environment and its exit status can be used for $error_status
+			# the build's exit status with 'wait' and use it for $error_status
 			rm -f $o.fifo
 			mkfifo -m 600 $o.fifo || exit
 			(
@@ -4017,14 +4017,15 @@ capture() # file command ...
 				# unlink early
 				exec rm $o.fifo
 			) &
-			$TEE -a $o < $o.fifo &
+			(
-			{
 				case $s in
 				?*)	echo "$s"  ;;
 				esac
 				showenv $action
 				"$@"
-			} < /dev/null > $o.fifo 2>&1
+			) < /dev/null > $o.fifo 2>&1 &
+			$TEE -a $o < $o.fifo
+			wait $!  # obtain exit status from build
 			;;
 		*)	{
 				case $s in

src/cmd/INIT/package.sh

@@ -4008,8 +4008,8 @@ capture() # file command ...
 		0)	if	executable ! $TEE
 			then	TEE=tee
 			fi
-			# Connect 'tee' to a FIFO instead of a pipe, so that the build is invoked from
+			# Connect 'tee' to a FIFO instead of a pipe, so that we can obtain
-			# the main shell environment and its exit status can be used for $error_status
+			# the build's exit status with 'wait' and use it for $error_status
 			rm -f $o.fifo
 			mkfifo -m 600 $o.fifo || exit
 			(
@@ -4017,14 +4017,15 @@ capture() # file command ...
 				# unlink early
 				exec rm $o.fifo
 			) &
-			$TEE -a $o < $o.fifo &
+			(
-			{
 				case $s in
 				?*)	echo "$s"  ;;
 				esac
 				showenv $action
 				"$@"
-			} < /dev/null > $o.fifo 2>&1
+			) < /dev/null > $o.fifo 2>&1 &
+			$TEE -a $o < $o.fifo
+			wait $!  # obtain exit status from build
 			;;
 		*)	{
 				case $s in