create-temporary-file and create-temporary-directory are subject to race conditions

[Mario Domenech Goulart]

Both use the non-atomic strategy of checking if a file system object exists then act, which may lead to race conditions.

create-temporary-directory is specially more fragile because it uses directory-exists? to check if a file system object exists. So, for example, if a regular file with the same name as the attempted one exists, create-temporary-directory will fail.