Silence warnings: Remove all unused local variables

Bug: b/123933266
Change-Id: If8fa478aa65f5c0046ca635a8d133911f8a59977
Reviewed-on: https://swiftshader-review.googlesource.com/c/25010
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>
Tested-by: Ben Clayton <bclayton@google.com>
diff --git a/src/OpenGL/libEGL/libEGL.cpp b/src/OpenGL/libEGL/libEGL.cpp
index 5c561b9..ffbe929 100644
--- a/src/OpenGL/libEGL/libEGL.cpp
+++ b/src/OpenGL/libEGL/libEGL.cpp
@@ -1148,6 +1148,8 @@
 	}
 
 	EGLenum imagePreserved = EGL_FALSE;
+	(void)imagePreserved; // currently unused
+
 	GLuint textureLevel = 0;
 	if(attrib_list)
 	{