Ensure version generated from date time is below 0xFFFF to prevent
modulo 65536 of the generated value causing failure to work out the time at
which the design was generated.

Remove the need to update the unique-design-version entry in the build
option YAML file between builds to ensure successful FPGA programming.
An FPGA design version based on the date and time is generated when no
unique-design-version is specified simplifying interactive build/debug
cycles.

Signed-off-by: Robert Nelson <robertcnelson@gmail.com>

BeagleV-Fire uses the PolarFire-Soc IAP feature to reprogram the
SoC-FPGA from Linux. The IAP mode used only actually programs the device
if the Libero design version is different from the one in the currently
programmed FPGA design.
This change to the gateware builder uses the gateware repo's git hash to
generate a Libero design version number which will be different with each
push to a forked gateware repository. This results in the bitstream
generated by the CI to successfully reprogram the SoC-FPGA after each
change to the gateware source code.

Set CI tag to libero-soc-v2023.2 to execute CI on gitlab runners using version
2023.2 of Libero.

Correct the location of the gateware source code in the script that
generates the device tree overlay for the gateware.

The build configuration YAML files describing a custom gateware
configuration will be used by the CI system generate bitstreams for user
custom FPGA designs.

First argument removed from gateware-builds-tester script.