Fix vulkan_backend linking in Android demo app (#2872)

Summary:
Pull Request resolved: #2872

## Context

Fix how `vulkan_backend` gets linked to the LLaMa demo app JNI.

imported-using-ghimport

Test Plan: Imported from OSS

Reviewed By: kirklandsign

Differential Revision: D55805378

Pulled By: SS-JIA

fbshipit-source-id: a6e3fa021d2e1dca19b2eafd2647a6bfbdd13ac1

Author: SS-JIA

extension/android/CMakeLists.txt

@@ -43,8 +43,9 @@ if(TARGET xnnpack_backend)
   target_link_options_shared_lib(xnnpack_backend)
   list(APPEND link_libraries xnnpack_backend XNNPACK pthreadpool cpuinfo)
 endif()
-if(TARGET vulkan_executor_runner_lib)
-  list(APPEND link_libraries vulkan_executor_runner_lib)
+if(TARGET vulkan_backend)
+  target_link_options_shared_lib(vulkan_backend)
+  list(APPEND link_libraries vulkan_backend)
 endif()
 
 add_library(executorch_jni SHARED jni/jni_layer.cpp)