Headers of libui is moved to the local directory

This makes clients of libui to be compiled without depending on global
headers.

Bug: 37731063
Test: sailfish build and boots
Test: 'BOARD_VNDK_VERSION=current m libui' successful
Change-Id: I6546f57964f2103bf3534fb8266fee4fb7d4678a
diff --git a/libs/ui/Android.bp b/libs/ui/Android.bp
index 8795322..d9cfed7 100644
--- a/libs/ui/Android.bp
+++ b/libs/ui/Android.bp
@@ -91,6 +91,8 @@
         "libnativebase_headers",
     ],
 
+    export_include_dirs: ["include"],
+
     export_static_lib_headers: [
         "libarect",
         "libmath",