We don't have to generate a temp name ourselves, it'll be done in apr_global_mutex_create().
We don't have to provide a filename, apr_global_mutex_create() generates one automatically.
Moreover, under Unix & Windows, the preferred mechanism won't use a file at all.
apr_file_mktemp() cannot be used as it creates the file (at least on FreeBSD).
Discussion in Apache mailing list: https://lists.apache.org/thread/ykb26kg4lgcqnldvxwd9p6hv16fy4z9l
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