Marc, I can probably be persuaded to check for fixed OpenBSD earlier (if we have a version number that can guarantee a fix, the better). But it would really help if you showed some minimal cooperation by proving to me that, as you claimed, the install-sh script (which scriptversion?) contained a race that was apparent on OpenBSD. In a way that's suitable for a bug report.
Did I already mention that (at least with Automake 1.10 and Autoconf 2.60+) it should be possible to workaround using ./configure "MKDIR_P=/usr/bin/mkdir -p" or "ac_cv_path_mkdir=/usr/bin/mkdir"? Thanks, Ralf