treewide: move build helper to more fitting places

Change-Id: I3d0cfe9283222d403ae369ec9db09201ad511e15
Reviewed-on: https://review.monogon.dev/c/monogon/+/3327
Reviewed-by: Serge Bazanski <serge@monogon.tech>
Tested-by: Jenkins CI
diff --git a/osbase/build/kconfig-patcher/kconfig-patcher.bzl b/osbase/build/kconfig-patcher/kconfig-patcher.bzl
new file mode 100644
index 0000000..39e786e
--- /dev/null
+++ b/osbase/build/kconfig-patcher/kconfig-patcher.bzl
@@ -0,0 +1,33 @@
+#  Copyright 2020 The Monogon Project Authors.
+#
+#  SPDX-License-Identifier: Apache-2.0
+#
+#  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.
+
+"""Override configs in a Linux kernel Kconfig
+"""
+
+def kconfig_patch(name, src, out, override_configs, **kwargs):
+    native.genrule(
+        name = name,
+        srcs = [src],
+        outs = [out],
+        tools = [
+            "//osbase/build/kconfig-patcher",
+        ],
+        cmd = """
+        $(location //osbase/build/kconfig-patcher) \
+            -in $< -out $@ '%s'
+        """ % struct(overrides = override_configs).to_json(),
+        **kwargs
+    )