Vulkan/OpenGL: log dlerror for loading updatable gfx driver

Test: build
Change-Id: Ifcb57266f5d93767ba911f70695e0bbbeace98e6
diff --git a/vulkan/libvulkan/driver.cpp b/vulkan/libvulkan/driver.cpp
index 6f09a8c..d7fdab5 100644
--- a/vulkan/libvulkan/driver.cpp
+++ b/vulkan/libvulkan/driver.cpp
@@ -183,6 +183,8 @@
                 .library_namespace = library_namespace,
             };
             so = android_dlopen_ext(lib_name.c_str(), LIB_DL_FLAGS, &dlextinfo);
+            ALOGE("Could not load %s from updatable gfx driver namespace: %s.",
+                  lib_name.c_str(), dlerror());
         } else {
             // load built-in driver
             so = android_load_sphal_library(lib_name.c_str(), LIB_DL_FLAGS);