Install doesn't obey GST_PLUGIN_DIR
Per the documentation (https://gstreamer.freedesktop.org/documentation/plugin-development/basics/boiler.html?gi-language=c) and the README file. One should be able to set GST_PLUGIN_DIR and then sudo ninja -C build install should install into the correct directory. This doesn't work. It always installs the plugin into /usr/local/lib/x86_64-linux-gnu/gstreamer-1.0.
This happens on Ubuntu 18.04 LTS.
Is there an alternative way of setting the output directory?