Added GLFW error-callback into FlutterEmbedderGLFW (#19998)

GLFW Error callback useful to clarify reasons of 'glfwInit()' failure.

On some platforms/desktop environments may be really strange failure reasons, like (in my case): "Linux: Failed to initialize inotify: Too many open files", so descriptive error messages helps to solve problem.

Author: inobelar

examples/glfw/FlutterEmbedderGLFW.cc

@@ -129,6 +129,10 @@ void printUsage() {
             << std::endl;
 }
 
+void GLFW_ErrorCallback(int error, const char* description) {
+  std::cout << "GLFW Error: (" << error << ") " << description << std::endl;
+}
+
 int main(int argc, const char* argv[]) {
   if (argc != 3) {
     printUsage();
@@ -138,6 +142,8 @@ int main(int argc, const char* argv[]) {
   std::string project_path = argv[1];
   std::string icudtl_path = argv[2];
 
+  glfwSetErrorCallback(GLFW_ErrorCallback);
+
   int result = glfwInit();
   assert(result == GLFW_TRUE);