libdl is a filter on libc, and pretty lightweight. Add it to the 'clibs'
package with libc, effectively tying them together in a pkgbase world.
Reviewed by: gjb
MFC after: 3 days
Differential Revision: https://reviews.freebsd.org/D13997
Create libdl.so.1 as a filter for libc.so.7 which exports public dl*
functions. The functions are resolved from the rtld instead, the goal
of creating library is to avoid errors from the static linker due to
missed libdl. For static binaries, an empty .o is compiled into
libdl.a so that static binaries still get dl stubs from libc.a.
Right now lld cannot create filter objects, disable libdl on arm64
when binutils are not used.
Reviewed by: bdrewery, dim (previos version); emaste
Exp run: PR 220525, done by antoine
Sponsored by: The FreeBSD Foundation
MFC after: 1 month
Differential revision: https://reviews.freebsd.org/D11504
