Apply @rcurtin modification to check STB version

Signed-off-by: Omar Shrit <omar@shrit.me>

CMake/stb/b.cpp

@@ -0,0 +1,15 @@
+#include "b.hpp"
+
+// Include the static implementation of all STB functions.
+#define STB_IMAGE_STATIC
+#define STB_IMAGE_IMPLEMENTATION
+#define STB_IMAGE_WRITE_STATIC
+#define STB_IMAGE_WRITE_IMPLEMENTATION
+
+#include <stb_image.h>
+#include <stb_image_write.h>
+
+void B::B()
+{
+  // Do nothing, just to check if the STB library is a working version.
+}