configure: simplify creation of plugin symbol list

configure: simplify creation of plugin symbol list

--dynamic-list is present on all supported ELF (not Windows or Darwin)
platforms, since it dates back to 2006; -exported_symbols_list is
likewise present on all supported versions of macOS.  Do not bother
doing a functional test in configure.

Remove the file creation from configure as well: for Darwin, move the
the creation of the Darwin-formatted symbols to meson; for ELF, use the
file in the source path directly and switch from -Wl, to -Xlinker to
not break weird paths that include a comma.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>