The configure script in gst-plugin defines some standard arguments for libtool
(in the GST_PLUGIN_LDFLAGS variable), used to build all plugins.  One of these
arguments is -export-symbols-regex, used to determine which symbols should be
made public from the plugin.

The problem is that the regex used, which is parsed internally by libtool using
egrep, is not recognized by NetBSD's native grep(1) utility.  The neat result of
this is that _no_ symbols are exported from plugins.

The regex contains {gst_,Gst,GST_}, which is the block not recognized by grep
(it is beeing treated as a simple literal string).  As an example (using the
whole regex):

[dawn jmmv] $ echo '{gst_,Gst,GST_}foobar' | grep '[_]*{gst_,Gst,GST_}.*'
{gst_,Gst,GST_}foobar
[dawn jmmv] $ echo 'gst_' | grep '[_]*{gst_,Gst,GST_}.*'
[dawn jmmv] $

I've fixed it by changing the regex to '[_]*(gst_|Gst|GST_).*'.  Patch attached
for this.

[dawn jmmv] $ echo 'gst_foobar' | grep -E '[_]*(gst_|Gst|GST_).*'
gst_foobar