tests: check_selftest: make sure we extract the base name

For C files we are trimming the .c from the needle, but then
still use path in the search. So the .c suffix remains leading
to:

  tools/testing/selftests/net/af_unix/so_peek_off.c not found in Makefile
  so_peek_off.c not found in .gitignore

Signed-off-by: Jakub Kicinski <[email protected]>

Author: kuba-moo

tests/patch/check_selftest/test.py

@@ -42,8 +42,8 @@ def check_new_files_makefile(tree, new_files, log):
             log.append("makefile inclusion check ignoring " + path)
             continue
 
+        needle = os.path.basename(needle)
         makefile = os.path.dirname(path) + "/Makefile"
-        needle = os.path.basename(path)
 
         cmd = ["git", "grep", needle, "--", makefile]
         result = subprocess.run(cmd, cwd=tree.path, capture_output=True,
@@ -72,8 +72,8 @@ def check_new_files_gitignore(tree, new_files, log):
             log.append("gitignore check ignoring " + path)
             continue
 
+        needle = os.path.basename(needle)
         target = os.path.dirname(path) + "/.gitignore"
-        needle = os.path.basename(path)
 
         cmd = ["git", "grep", needle, "--", target]
         result = subprocess.run(cmd, cwd=tree.path, capture_output=True,