apps/gl: Add test for reading from shadow memory

The main purpose of this test is to verify the correctness of reading
of the coherent memory after it was written to from GPU.

Signed-off-by: Illia Iorin <[email protected]>

Author: Illia Iorin

apps/gl/.gitignore

@@ -1,5 +1,6 @@
 child
 compiled_vertex_array
+coherent_memory_read
 config
 coherent_memory_write
 debug

apps/gl/CMakeLists.txt

@@ -19,6 +19,7 @@ set (targets
     config
     coherent_memory_write
     compiled_vertex_array
+    coherent_memory_read
     debug
     default
     dlopen