fix: Provide support for the platform linux/arm64

[jcfitzpatrick12]

The last PR got polluted with some other commits. This fresh PR includes only the original changes.

Solve build errors when building from source on the platform linux/arm64. Validated using this Dockerfile (placed in the root directory of the project):

FROM ubuntu:22.04 AS base

RUN apt-get update && apt-get install -y \
    libusb-1.0 \
    libfftw3-dev \
    libsoapysdr-dev

FROM base AS build

RUN apt-get update && apt-get install -y \
    git \
    cmake \
    build-essential \
    pkg-config

WORKDIR /tmp

COPY . ExtIO_sddc/

RUN cd ExtIO_sddc && \
    mkdir build && \
    cd build && \
    cmake .. -DCMAKE_INSTALL_PREFIX=/opt/ExtIO_sddc && \
    make && \
    make install && \
    mkdir -p /opt/ExtIO_sddc/bin && \
    cp unittest/unittest /opt/ExtIO_sddc/bin/unittest

FROM base AS runtime

COPY --from=build /opt/ExtIO_sddc/bin/unittest /usr/local/bin/unittest

CMD ["unittest"]

To build an image:

docker buildx build --platform linux/arm64 --tag extio_sddc:mre --target runtime . --load

And running a container from it:

docker run --platform linux/arm64  extio_sddc:mre
Running 9 test cases...
decimate=0 nxfers=201 count=8 totalsize=262144
decimate=1 nxfers=195 count=16 totalsize=524288
decimate=2 nxfers=181 count=27 totalsize=884736
decimate=3 nxfers=160 count=46 totalsize=1507328
decimate=4 nxfers=135 count=69 totalsize=2260992
Complete.
    Passed:  9
    Failed:  0
    Skipped: 0

In the same way, the build and unit tests succeed using the platform linux/amd64.