"subdirmk: $sdmk unexpectedly exists (${dir_prefix} not mentioned on subdirmk/generate command line, maybe directory is missing from SUBDIRMK_SUBDIRS)";
if (stat $sdmk) {
die
"subdirmk: $sdmk unexpectedly exists (${dir_prefix} not mentioned on subdirmk/generate command line, maybe directory is missing from SUBDIRMK_SUBDIRS)";