Move libipchecksum to frameworks/libs/net.

This code is used by the DNS resolver mainline module, so it
should be in a directory that is automerged to sc-mainline-prod,
not in /system/core.

Test: m
Change-Id: I2d953afa3d2766ca2b4529e9e49151c098b466aa
diff --git a/staticlibs/native/ip_checksum/Android.bp b/staticlibs/native/ip_checksum/Android.bp
new file mode 100644
index 0000000..d7e195d
--- /dev/null
+++ b/staticlibs/native/ip_checksum/Android.bp
@@ -0,0 +1,40 @@
+// Copyright (C) 2021 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.
+
+package {
+    default_applicable_licenses: ["Android-Apache-2.0"],
+}
+
+cc_library_static {
+    name: "libip_checksum",
+
+    srcs: [
+        "checksum.c",
+    ],
+
+    cflags: [
+        "-Wall",
+        "-Werror",
+    ],
+
+    export_include_dirs: ["."],
+
+    // Needed because libnetutils depends on libip_checksum, and libnetutils has
+    // vendor_available = true. Making this library vendor_available does not create any maintenance
+    // burden or version skew issues because this library is only static, not dynamic, and thus is
+    // not installed on the device.
+    //
+    // TODO: delete libnetutils from the VNDK in T, and remove this.
+    vendor_available: true,
+}