Add Vivado Block Design support for simulation

[SzymonHitachi]

Reopening #962 after cleanup and alignment.

Closes #963

[monkey265]

If this gets added, wont it break pre-existing project using extract_compile_order.tcl?

[yahya-farhadi]

If this gets added, wont it break pre-existing project using extract_compile_order.tcl?

Hi,
No, Vivado issues a warning (not an error) when no files match the glob, so the script continues execution. The generate_target call simply receives an empty list and becomes a no-op.

However, for projects without block designs, this will produce a spurious WARNING: [Vivado 12-818] No files matched '*.bd' in the output, which could be confusing to users. Adding -quiet would suppress that unnecessary warning:

line 9: generate_target {simulation synthesis} [get_files -quiet *.bd]
line 12: foreach bd [get_files -quiet *.bd]  {    
                  open_bd_design ${bd}
            }

So: not a breaking change, but a minor cosmetic issue (noisy warnings) that -quiet would clean up.
Good to add -quiet in line 9 and line 12.