Updated ghdl_interface.py per #458

[GlenNicholls]

This update allows a TCL script to be passed to GTKWave when the -g flag is passed if the environment has the set_sim_option('ghdl.init_file.gui', '<fileName>.tcl') set. The limitation is that only a single file can be passed, however <fileName>.tcl can source other TCL scripts if desired.

[GlenNicholls]

Another thing to note is that ghdl.init_file.gui might be better suited as gtkwave.init_file.gui to avoid confusion, but I left it using the interface name for simplicity.

[kraigher]

As you mentioned it would be good if the name conveyed that gtkwave was involved. Maybe calling the sim_option ghdl.gtkwave_script would be better.

Also the sim option should be mentioned in the documentation. The source for the documentation is within ui.py where there is a list of sim options in a docstring. Just adding the new option there with a small description is enough.

[kraigher]

I do not see how vunit_tb_path tcl variable is available so this documentation is inaccurate. Maybe copy paste error?

[GlenNicholls]

Yep, sorry about that

Suggested change

During script evaluation the ``vunit_tb_path`` variable is defined

[umarcor]

I tried adding vu.set_sim_option('ghdl.gtkwave_script.gui', 'addWave.tcl') to my run.py, where addWave.tcl is #455 (comment). It fails with:

GTKWave Analyzer v3.3.101 (w)1999-2019 BSI

[0] start time.
[1400000000] end time.
GTKWAVE | Executing Tcl script '"/src/addWave.tcl"'
GTKWAVE | couldn't read file ""/src/addWave.tcl"": no such file or directory
WM Destroy

However, if I replace https://github.com/VUnit/vunit/blob/master/vunit/ghdl_interface.py#L276 with cmd += ["--script", "{}".format(abspath(init_file))], it works as expected.

@GlenNicholls, might those additional double quotes be platform-dependent?