[generate.py] Override blob list if it already exists (#1635)

Before, generate.py appended the list at the end of the output file.
When running the cmake configuration steps multiple times on the
examples, the blob list (such as fwd_blob_list.txt) would grow at every
configuration.
`library/src/tensor_operation_instance/gpu/mha/CMakeLists.txt` worked around
this issue by removing the output file if it exists.

Now, generate.py overrides the content of the output file.
There is no need for the workaround in the CMakeLists.txt;
and the issue is solved for the example projects too.

[ROCm/composable_kernel commit: 464abd235e]

example/ck_tile/01_fmha/generate.py

@@ -47,6 +47,9 @@ def list_blobs(output_file : Optional[str], api_list : List[str], kernel_filter
     assert output_file is not None
     file_path = Path(output_file)
 
+    # create an empty file / drop its contents if it exists
+    open(file_path, "w").close()
+
     for api in api_list:
         handler = handlers[api][HandlerId.LIST_BLOBS]
         handler(file_path, kernel_filter, receipt, mask_impl)

example/ck_tile/02_layernorm2d/generate.py

@@ -559,7 +559,7 @@ float layernorm2d_fwd(layernorm2d_fwd_traits t,
         w_p = Path(self.working_path)
         list_p = w_p / 'layernorm2d_fwd_blobs.txt'
         blobs = self.get_blobs()
-        with list_p.open('a') as list_f:
+        with list_p.open('w') as list_f:
             # api related file
             list_f.write(str(w_p / (self.name_api + ".cpp"))  + "\n")
             list_f.write(str(w_p / (self.name_common_header + ".hpp"))  + "\n")

library/src/tensor_operation_instance/gpu/mha/CMakeLists.txt

@@ -27,11 +27,6 @@ rocm_install(FILES ${MHA_HEADERS} DESTINATION include/ck_tile/ops)
 # headers for building lib
 file(COPY ${MHA_HEADERS} DESTINATION ${FMHA_CPP_FOLDER})
 
-# Delete the blob file if it exists to avoid append of old content.
-if(EXISTS ${FMHA_CPP_FOLDER}/blob_list.txt)
-    file(REMOVE ${FMHA_CPP_FOLDER}/blob_list.txt)
-endif()
-
 set(FMHA_KNOWN_APIS "fwd,fwd_splitkv,fwd_appendkv,bwd")
 
 # generate a list of kernels, but not actually emit files at config stage