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/shaders/Android.bp b/libs/shaders/Android.bp
index 390b228..1cd143e 100644
--- a/libs/shaders/Android.bp
+++ b/libs/shaders/Android.bp
@@ -38,6 +38,10 @@
         "libui-types",
     ],
 
+    header_libs: [
+        "libtonemap_headers",
+    ],
+
     srcs: [
         "shaders.cpp",
     ],