Doc tests fail to run in from-source build

[abrown]

While investigating failures such as this one, I discovered that the library path is not set up correctly in the doc tests for the "build from source" option, a change introduced in 68d5a48. This means that the system linker can't find the openvino libraries and so the test fails with:

/tmp/rustdoctestT9kb6s/rust_out: error while loading shared libraries: libinference_engine_c_api.so: cannot open shared object file: No such file or directory

What is interesting is that the other tests (--lib and --tests) both work correctly. I'm unsure what is different when running the doc tests so I have disabled them for the time being in the from-source build (they are enabled for all of the rest of the CI tasks).

Here is a Dockerfile that should reproduce the failure:

FROM ubuntu
WORKDIR /usr/src
# Install packages as in .github/workflows/main.yml
RUN apt update && apt install -y clang cmake libclang-dev gnupg2 libdrm2 libglib2.0-0 libusb-1.0-0-dev lsb-release libgtk-3-0 libtool udev unzip dos2unix
# Install other necessary packages (apparently present on GitHub runners)
RUN apt install -y git git-lfs curl python
# Install Rust
RUN curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
# Pull and build the project
RUN git clone --depth 1 --recursive --branch finder https://github.com/abrown/openvino-rs
WORKDIR /usr/src/openvino-rs
RUN source $HOME/.cargo/env && cargo test -vv --features openvino-sys/from-source