dajiaohuang
`build-subsets.sh` appears to skip cleanup when the temporary source directory already exists: ```sh if ! [ -d "$TEMP_SOURCE" ]; then rm -rf $TEMP_SOURCE fi mkdir $TEMP_SOURCE ``` When `source/temp` is left by an interrupted or previously failed run, the condition is false, so the directory is not removed and the following `mkdir` fails. Please invert the condition (or remove the directory unconditionally before recreating it) and add a repeat-build regression check. The relevant lines are 169-175 on the current default branch.