Migrate libandroid headers to ndk_headers.

Test: make native
Bug: http://b/30465923
Change-Id: I0ef0b3630670241c4efd22515b6ab13eb41a81b3
diff --git a/Android.bp b/Android.bp
index 4c1cafc..f5620f8 100644
--- a/Android.bp
+++ b/Android.bp
@@ -1,3 +1,10 @@
+ndk_headers {
+    name: "libandroid_headers",
+    from: "include/android",
+    to: "android",
+    srcs: ["include/android/**/*.h"],
+}
+
 subdirs = [
     "cmds/*",
     "libs/*",