[blog/bgpscanner-backwards-compat] Mention how to enable the legacy script

content/blog/bgpscanner-backwards-compat.md

@@ -72,6 +72,15 @@ how to convert an old invocation to the new format.
 True, it might not be the best, most expressive, most idiomatic way to write the query,
 but it is an excellent starting point.
 
+You can install the `bgpscanner` legacy wrapper script along with other µbgpsuite
+tools by enabling the `bgpscanner-legacy` configuration option with `meson`,
+just run:
+```sh
+$ meson configure -Dbgpscanner-legacy=true
+```
+inside your µbgpsuite build directory and it will be installed along with the
+other tools upon `ninja install`.
+
 Obviously, it wouldn't be a true announcement post, if I didn't also mention
 that the `bgpscanner` legacy wrapper script is documented in its own fantastic
 man [page](https://git.doublefourteen.io/bgp/ubgpsuite/src/branch/master/tools/bgpscanner/bgpscanner.1.in).