compat: Add libutils shim

* This is required because some old libraries still rely on the
  strncpy16() function.

Change-Id: I77da329d1296d946f43ffe6708444b1d25607342

Android.bp

@@ -335,6 +335,14 @@ cc_library_shared {
     vendor_available: true,
 }
 
+cc_library_shared {
+    name: "libutils_shim",
+    shared_libs: ["libutils"],
+    srcs: ["libutils/String16.cpp"],
+    system_ext_specific: true,
+    vendor_available: true,
+}
+
 cc_library {
     name: "libip_checksum_shim",
     whole_static_libs: [

libutils/String16.cpp

@@ -0,0 +1,22 @@
+/*
+ * Copyright (C) 2023 The LineageOS Project
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <stdio.h>
+
+extern "C" {
+char16_t* strncpy16(char16_t* dst, const char16_t* src, size_t n) {
+    char16_t* q = dst;
+    const char16_t* p = src;
+    char ch;
+    while (n) {
+        n--;
+        *q++ = ch = *p++;
+        if (!ch) break;
+    }
+    *q = 0;
+    return dst;
+}
+}