Share JNI file descriptor helper code

Move JNI File descriptor code from NetworkStack into a common native
static library.

Bug: 158749603
Test: atest NetworkStaticLibTests / treehugger
Change-Id: I3d14587ee8e8590b727736d7d2e29cba687e5514
diff --git a/staticlibs/native/netjniutils/Android.bp b/staticlibs/native/netjniutils/Android.bp
new file mode 100644
index 0000000..8417c52
--- /dev/null
+++ b/staticlibs/native/netjniutils/Android.bp
@@ -0,0 +1,34 @@
+// Copyright (C) 2020 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.
+
+cc_library_static {
+    name: "libnetjniutils",
+    srcs: ["netjniutils.cpp"],
+    header_libs: ["jni_headers"],
+    shared_libs: ["liblog"],
+    export_header_lib_headers: ["jni_headers"],
+    export_include_dirs: ["include"],
+    cflags: [
+        "-Wall",
+        "-Werror",
+        "-Wno-unused-parameter",
+    ],
+    sdk_version: "29",
+    min_sdk_version: "29",
+    apex_available: [
+        "//apex_available:anyapex",
+        "//apex_available:platform",
+    ],
+    visibility: ["//visibility:public"],
+}