init: Refactor selinux.h/cpp

This change factors out functions that handle selabels from
selinux.h/cpp into selabel.h/cpp.  This allows util.cpp to be used by
the upcoming native zygote without a bunch of define flags that are
required for selinux.cpp.

Bug: 133443795
Test: Build and boot cuttlefish.
Change-Id: Ie238a96c6407c6698a605dd8803c1727abfaae7b
diff --git a/init/selabel.h b/init/selabel.h
new file mode 100644
index 0000000..5d590b2
--- /dev/null
+++ b/init/selabel.h
@@ -0,0 +1,32 @@
+/*
+ * Copyright (C) 2019 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.
+ */
+
+#pragma once
+
+#include <string>
+#include <vector>
+
+namespace android {
+namespace init {
+
+void SelabelInitialize();
+bool SelabelLookupFileContext(const std::string& key, int type, std::string* result);
+bool SelabelLookupFileContextBestMatch(const std::string& key,
+                                       const std::vector<std::string>& aliases, int type,
+                                       std::string* result);
+
+}  // namespace init
+}  // namespace android