Add a bpf_tethering_headers lib used by the programs and JNI.

This provides a place to store common definitions that can be
used by both the programs and by JNI code in the tethering
module.

Over time much of the tethering-specific code in bpf_shared.h
could move here.

Test: m
Bug: 177884581
Change-Id: I4bf2c762d61cd5db003d59880e6bf7d107ff1a07
diff --git a/Tethering/bpf_progs/Android.bp b/Tethering/bpf_progs/Android.bp
index d62e9a1..b06528b 100644
--- a/Tethering/bpf_progs/Android.bp
+++ b/Tethering/bpf_progs/Android.bp
@@ -15,6 +15,26 @@
 //
 
 //
+// struct definitions shared with JNI
+//
+cc_library_headers {
+    name: "bpf_tethering_headers",
+    vendor_available: false,
+    host_supported: false,
+    export_include_dirs: ["."],
+    cflags: [
+        "-Wall",
+        "-Werror",
+    ],
+    sdk_version: "30",
+    min_sdk_version: "30",
+    apex_available: ["com.android.tethering"],
+    visibility: [
+        "//packages/modules/Connectivity/Tethering",
+    ],
+}
+
+//
 // bpf kernel programs
 //
 bpf {