Shell: Add some tests for builtin redirection

Author: https://github.com/alimpfard
Commit: 154ffa3f5f
Pull-request: https://github.com/SerenityOS/serenity/pull/3144
Issue: https://github.com/SerenityOS/serenity/issues/3072
Reviewed-by: https://github.com/awesomekling

Shell/Tests/builtin-redir.sh

@@ -0,0 +1,17 @@
+#!/bin/sh
+
+rm -rf shell-test
+mkdir -p shell-test
+cd shell-test
+
+    time sleep 1 2>timeerr >timeout
+    cat timeout
+    # We cannot be sure about the values, so just assert that they're not empty.
+    test -n "$(cat timeerr)" || echo "Failure: 'time' stderr output not redirected correctly" && exit 1
+    test -e timeout || echo "Failure: 'time' stdout output not redirected correctly" && exit 1
+
+    time ls 2> /dev/null | head > timeout
+    test -n "$(cat timeout)" || echo "Failure: 'time' stdout not piped correctly" && exit 1
+
+cd ..
+rm -rf shell-test # TODO: Remove this file at the end once we have `trap'