sh testsuite: add tests for exitcode on failure to exec

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/shell/ash_test/ash-misc/exitcode_EACCES.right b/shell/ash_test/ash-misc/exitcode_EACCES.right
new file mode 100644
index 0000000..0a332f5
--- /dev/null
+++ b/shell/ash_test/ash-misc/exitcode_EACCES.right
@@ -0,0 +1,2 @@
+exitcode_EACCES.tests: line 1: ./: Permission denied
+126