ash: fix $! value when traps are set

Signed-off-by: Alexander Shishkin <virtuoso@slind.org>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

shell/ash_test/ash-signals/signal7.right

@@ -0,0 +1 @@
+Bug detected: 0

shell/ash_test/ash-signals/signal7.tests

@@ -0,0 +1,18 @@
+bug() {
+	trap : exit
+	# Bug was causing sh to be run in subshell,
+	# as if this line is replaced with (sh -c ...; exit $?) &
+	# here:
+	sh -c 'echo REAL_CHILD=$$' &
+	echo PARENTS_IDEA_OF_CHILD=$!
+	wait  # make sure bkgd shell completes
+}
+
+bug | {
+while read varval; do
+	eval $varval
+done
+test x"$REAL_CHILD" != x"" \
+&& test x"$REAL_CHILD" = x"$PARENTS_IDEA_OF_CHILD"
+echo "Bug detected: $?"
+}