ash: do not leave SIGQUIT ignored on "exec CMD"

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/shell/ash_test/ash-signals/sigquit_exec.tests b/shell/ash_test/ash-signals/sigquit_exec.tests
new file mode 100755
index 0000000..24bda69
--- /dev/null
+++ b/shell/ash_test/ash-signals/sigquit_exec.tests
@@ -0,0 +1,4 @@
+# Should show no masked signals in both cases.
+# We had a bug where SIGQUIT was masked on exec.
+grep SigIgn: /proc/self/status
+exec grep SigIgn: /proc/self/status