Stop crypt($tied,...) from calling FETCH twice

It was doing so if FETCH returned a UTF8 string the first time.  It
then turned on the UTF8 flag on the result of the second FETCH, even
if it wasn’t UTF8:

$ ./miniperl -e 'sub TIESCALAR{bless[substr(chr 256,0,0), chr 255]} sub FETCH{shift @{$_[0]}}tie $t, ""; crypt $t, ""'
Wide character in crypt at -e line 1.

(There are no wide characters fed to crypt() there.)
tie.t: Don’t skip base.pm test unconditionally

but only if we are under miniperl and base has not been built yet.

I made a mistake in 19295df3 by omitting the ?.  Thanks to Karl
Williamson for noticing it.