Declare the headers of the ndk_library

This creates a dependency edge between the ndk_library and its headers,
which should be a no-op in regular Soong builds. This dependency edge
will be used in the Multi-tree project to export the relevant .h files into a well
known location

Formatting changes are from bpfmt

Test: m nothing
Bug: 239044713
Change-Id: Id8db2858875a4aee904456fe3dec77c71fa47dc9

media/native/midi/Android.bp

@@ -74,4 +74,8 @@ ndk_library {
     symbol_file: "libamidi.map.txt",
 
     first_version: "29",
+    export_header_libs: [
+        "amidi",
+    ],
+
 }