This was because math/gsl installs 2 libraries, libgsl.so and
libgslcblas.so, the former of which should depend on the latter one.
Instead, the gsl package through its pkg-config script asks users to
link to both libraries. This fails when the link line also has
-Wl,--as-needed which causes the linker to drop the second library.
In such case the above error is triggered at runtime.
Also update WWW.
PR: 251206
Submitted by: Ned Leitch <ned.leitch+freebsd@gmail.com>
MFH: 2020Q4
a908650fe7