kbuild.jinja2: Keep modules name simpler and neutral

modules.tar.xz complicates jinja templates and probably add
some inflexibility in future, if we decide to change compression
format. It is better to avoid also dots in artifact name.
Additionally change compression to xz, and fix logic related
to artifact name vs file name.

Signed-off-by: Denys Fedoryshchenko <denys.f@collabora.com>

config/runtime/kbuild.jinja2

@@ -146,13 +146,15 @@ echo '# {command}' | tee -a {job_log}
         if storage and NODE:
             root_path = '-'.join([JOB_NAME, NODE['id']])
             print(f"[_upload_artifacts] Uploading artifacts to {root_path}")
-            for file_name, file_path in local_artifacts.items():
+            for artifact_name, file_path in local_artifacts.items():
+                file_name = os.path.basename(file_path)
+                print(f"[_upload_artifacts] Uploading [{artifact_name}] {file_name}")
                 if os.path.exists(file_path):
                     file_url = storage.upload_single(
                         (file_path, file_name), root_path
                     )
                     print(file_url)
-                    artifacts[file_name] = file_url
+                    artifacts[artifact_name] = file_url
         return artifacts
 
     def _fetch_firmware(self, src_path):
@@ -187,7 +189,7 @@ echo '# {command}' | tee -a {job_log}
             job_log: job_log_path,
             'config': os.path.join(src_path, '.config'),
             'bzImage': os.path.join(src_path, 'arch/x86/boot/bzImage'),
-            'modules.tar.gz': os.path.join(src_path, 'modules.tar.gz'),
+            'modules': os.path.join(src_path, 'modules.tar.xz'),
         }
 
         if os.path.exists(job_log_path):
@@ -204,7 +206,7 @@ echo '# {command}' | tee -a {job_log}
                 "INSTALL_MOD_STRIP=1",
                 "modules_install",
             ]),
-            'modules_tarball': "tar -C _modules_ -czf modules.tar.gz .",
+            'modules_tarball': "tar -C _modules_ -cJf modules.tar.xz .",
         }
         step_results = {name: (None, []) for name in steps.keys()}