ANDROID: export an include directory.

This allows including public header files defined by tpm2-tss.

Bug: 148102516
Test: Build other code using this
Change-Id: I1b234060a64f420863cb3dac7ee750af9dea1012
diff --git a/Android.bp b/Android.bp
index cf488c1..26c2e11 100644
--- a/Android.bp
+++ b/Android.bp
@@ -19,6 +19,9 @@
         "-DBSSL", // Use OpenSSL (BoringSSL) encryption instead of gcrypt
     ],
     vendor: true,
+    export_include_dirs: [
+        "include",
+    ],
 }
 
 cc_library {