Both of my IRIX machines have file-4.23 installed (Bug 232737 seems to have been resolved). (Bug 209623 suggests that I also managed to build file-4.25, but this is masked as being broken on my systems, and also no longer available in the portage tree) I haven't filed a bug on file-5.00 because I was never able to get it working - but I'll do that now...
Actually, having re-read Bug 209623 is looks as if gnulib built successfully, not file. Therefore file-4.23 is definitely the last-known-good version for IRIX.
*** This bug has been marked as a duplicate of bug 267075 ***