Configure script clears the dynamic linker search path on FreeBSD

[Daniel Eisele]

Hi,

while experimenting with ncurses on FreeBSD 13.0 I noticed that ./configure
clears the dynamic linker search path by executing "ldconfig -v" in order to
obtain cf_cv_ld_searchpath.

This leaves the user unable to run many applications (e.g. bash) because the
system then can't find the required shared libraries. This can be fixed by
running "service ldconfig restart".

One thing to note here, is that "ldconfig -v" behaves counterintuitively on
FreeBSD, which got fixed (with explanation) here:
  
https://cgit.freebsd.org/src/commit/sbin/ldconfig/ldconfig.c?id=3ede04c78c7c726ed79a39d22c65a58d0ecc5d00

This fix is not yet in any FreeBSD release version, but will be available on
FreeBSD 13.1.

With this fix "ldconfig -v" (now equivalent to "ldconfig -Rv") doesn't clear
the search path, however, still performs a rescan.

The FreeBSD ports collection works around this problem by adding this to env:
  cf_cv_ld_searchpath="${LOCALBASE}/lib /usr/lib /lib"

Regards,
Daniel Eisele