Fix newvers.sh with BUILD_WITH_STRICT_TMPPATH=1

[arichardson]

Summary

newvers.sh runs mkfifo which did not exist before this change.
However, I didn't notice before because it is run from a function
where a missing command does cause a noticeable failure.

[emaste]

LGTM. One of either @kib or @markj suggested eliminating the mkfifo but I believe we cannot without a more capable shell.

[markj]

Oh huh. What's the problem with:

$git_cmd ... | while read smode ...; do
...
done

? A quick test suggests that /bin/sh does indeed support that.

Anyway, LGTM.

[emaste]

Oh, maybe I'm conflating a different comment with something about mkfifo, but it was in D15968. In any case, the issue is that with cmd | while ... a return in the while loop returns from the subshell, not the function. There's a decent Stack Overflow discussion at https://stackoverflow.com/questions/13726764/while-loop-subshell-dilemma-in-bash