Using local build with gstreamer-rs

[Samyak]

Hey,
Please let me know if this is the wrong place to ask questions or if my
question has been answered before.

My question is I want to use a newer version of gstreamer with
gstreamer-rs. I am using gst-build to build a local version of gstreamer to
build the master branch and I want gstreamer-rs to use that instead of
using my global gstreamer which is on 1.18.

To give some context around my reasoning to use the master branch (I'm
giving this context so that I can get a better overall solution in case I'm
taking the wrong approach here). I am using Arch Linux which means I'm
using cuda 11.3.0-2. Based on this issue:
https://gitlab.freedesktop.org/gstreamer/gst-plugins-bad/-/issues/1469,
gstreamer 1.18 has issues with that. Because of this when I use
gst-inspect, I don't get cudascale or any of the cuda functions. When I use
gst-build to build the master branch, everything works when I try
gst-launch. But I want to actually use the gstreamer-rs bindings.
I have tried to clone the gstreamer-rs repo, and run the instructions from
here:
https://gitlab.freedesktop.org/gstreamer/gstreamer-rs/-/blob/master/DEVELOPMENT.md
and also set PKG_CONFIG env variable to the meson-private directory from
the gst-build. I then compiled using the v1_20 feature on Cargo and the
compilation worked. But, when I try using
gst::ElementFactory::make("cudaupload", Some("cudaupoad"), I get this
error:
BoolError { message: "Failed to create element from factory name",
filename: "<home_dir>/Documents/projects/gstreamer-rs/gstreamer/src/auto/
element_factory.rs", function: "gstreamer::auto::element_factory", line:
204 }', src/main.rs:10:82

Here's the full backtrace if that helps: https://pastebin.com/1U0qWWkH

Couple of questions on my end:
1. Do we know for a fact if gstreamer-rs is using my local build? How do I
verify this? It seems weird that when I run the devenv on gst-build I am
able to run cudascale with gst-launch but it does not seem to be working
with gstreamer-rs.
2. Am I writing the rust code wrong? Is elementfactory the wrong way to
create cuda elements on Rust?
3. Is there any sample I can refer to so maybe I can try reverse
engineering this? Or has gstreamer-rs never been tested with cuda support
before?

Feel free to suggest a completely different approach if I'm doing things
the wrong way.

Thanks!
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