[ET-VK][ez] Fix to codegen caching mechanism (#12274)

This PR was created by the merge bot to help merge the original PR into
the main branch.
ghstack PR number: #12272 by
@SS-JIA
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ghstack PR base:
https://github.com/pytorch/executorch/tree/gh/SS-JIA/253/base
ghstack PR head:
https://github.com/pytorch/executorch/tree/gh/SS-JIA/253/head
Merge bot PR base: https://github.com/pytorch/executorch/tree/main
Merge bot PR head:
https://github.com/pytorch/executorch/tree/gh/SS-JIA/253/orig
@diff-train-skip-merge

Co-authored-by: Stephen Jia <[email protected]>

Author: pytorchbot

backends/vulkan/runtime/gen_vulkan_spv.py

@@ -861,10 +861,6 @@ def generate_src_file(shader_paths_pair):
 
             # Construct generated file name
             gen_out_path = os.path.join(output_dir, f"{src_file_name}.{out_file_ext}")
-            # Construct path of cached generated file
-            cached_gen_out_path = os.path.join(
-                cache_dir, f"{src_file_name}.{out_file_ext}"
-            )
 
             # Execute codegen to generate the output file
             with codecs.open(src_file_fullpath, "r", encoding="utf-8") as input_file:
@@ -875,10 +871,6 @@ def generate_src_file(shader_paths_pair):
             with codecs.open(gen_out_path, "w", encoding="utf-8") as output_file:
                 output_file.write(output_text)
 
-            if cache_dir is not None:
-                # Store the generated file in the cache for SPIR-V compilation
-                shutil.copyfile(gen_out_path, cached_gen_out_path)
-
         def compile_spirv(shader_paths_pair):
             # Extract components from the input tuple
             # name of generated .glsl, .glslh, or .h
@@ -959,7 +951,10 @@ def compile_spirv(shader_paths_pair):
                     else:
                         raise RuntimeError(f"{err_msg_base} {e.stderr}") from e
 
+                # If compilation was successful, store the source GLSL file and the
+                # compiled SPIR-V file in the cache for future comparison.
                 if cache_dir is not None:
+                    shutil.copyfile(gen_out_path, cached_gen_out_path)
                     shutil.copyfile(spv_out_path, cached_spv_out_path)
 
             return (spv_out_path, gen_out_path)