Fix a bug in the Windows Builds:

With commit
80d6e681f ("MS Windows: Get a canonical paths name: Important if path length exceeds MAX_PATH, might happen when using  PDKs", 2025-04-12)
the newly introduced function get_windows_canonical_path() does not do the
right thing when the path name is only a simple file name. Then internally
used function GetFullPathNameW() then will prepend the current directory to the
file name, which may be simply wrong.

src/frontend/inpcom.c

@@ -9867,6 +9867,10 @@ char* get_windows_canonical_path(const char* input_path) {
         return NULL;
     }
 
+    /* If plain filename, just copy it. */
+    if (!strchr(input_path, '\\') && !strchr(input_path, '/'))
+        return copy(input_path);
+
     inputLenMB = (int)strlen(input_path);
 
     if (inputLenMB == 0) {