Previously, the build tools for the FPGA bitfiles would try and
autodetect the Vivado executable, but would allow for a `vivado_lab`
executable. However, Vivado Lab Edition can't build bitfiles nor run
testbenches. Its only use with the USRP FPGA build tooling is to run
`viv_jtag_program` and `viv_jtag_list` (which are command-line proxies
for probing FPGAs attached to JTAG, and for programming bitfiles over
JTAG, e.g. to an X3x0).
When Vivado Lab and Vivado were present, it was possible that we ran
into issues where Vivado Labs would be preferred, and then builds or
testbenches would fail.
We therefore remove the ability to use Vivado Lab. Running the Vivado
Lab Edition with the GUI, and loading and probing bitfiles is of course
still possible, but tools like `rfnoc_image_builder` can no longer
accidentally try to use Vivado Lab instead of regular Vivado.
Original-commit: 21c4c591a51d520c7aac7108e853e59c4953f953
Martin Braun
8e0831b348