export libtonemap headers

libtonemap could be overridden by the vendor counterpart. The
headers should come from framework.

Bug: 200310159
Change-Id: I2685903543aac8c2d02fee2deba2c40dbb2f287c
diff --git a/libs/renderengine/tests/Android.bp b/libs/renderengine/tests/Android.bp
index a426850..d91af1e 100644
--- a/libs/renderengine/tests/Android.bp
+++ b/libs/renderengine/tests/Android.bp
@@ -42,6 +42,9 @@
         "libshaders",
         "libtonemap",
     ],
+    header_libs: [
+        "libtonemap_headers",
+    ],
 
     shared_libs: [
         "libbase",