Record the image variant in each Dockerfile

docker/tensorrt/Dockerfile.amd64

@@ -25,6 +25,7 @@ RUN --mount=type=bind,from=trt-wheels,source=/trt-wheels,target=/deps/trt-wheels
     && pip3 install -U /deps/trt-wheels/*.whl
 
 COPY --from=rootfs / /
+ENV FRIGATE_IMAGE_VARIANT=tensorrt
 COPY docker/tensorrt/detector/rootfs/etc/ld.so.conf.d /etc/ld.so.conf.d
 RUN ldconfig
 

docker/tensorrt/Dockerfile.arm64

@@ -151,6 +151,7 @@ RUN --mount=type=bind,from=trt-wheels,source=/trt-wheels,target=/deps/trt-wheels
 
 WORKDIR /opt/frigate/
 COPY --from=rootfs / /
+ENV FRIGATE_IMAGE_VARIANT=tensorrt-jp6
 
 # Fixes "Error importing detector runtime: /usr/lib/aarch64-linux-gnu/libstdc++.so.6: cannot allocate memory in static TLS block"
 ENV LD_PRELOAD /usr/lib/aarch64-linux-gnu/libstdc++.so.6