Move aninja and overrideflags from shell functions to real scripts

Trying to clean up cruft from envsetup.sh

Shell functions require re-sourcing envsetup.sh, and should be avoided
if possible.

Bug: 340648588
Test: try the scripts
Change-Id: I15ec39b0382d9dd60e290dae633e8730a8d18131

bin/aninja

@@ -0,0 +1,25 @@
+#!/bin/bash -e
+
+# Copyright (C) 2022 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# Common script utilities
+source $(cd $(dirname $BASH_SOURCE) &> /dev/null && pwd)/../../make/shell_utils.sh
+
+require_top
+require_lunch
+
+cd $(gettop)
+prebuilts/build-tools/linux-x86/bin/ninja -f out/combined-${TARGET_PRODUCT}.ninja "$@"
+