run_lvspex.sh does not do full R-C parasitic extraction

[RTimothyEdwards]

The script openfasoc/common/drc-lvs-check does not perform full R-C parasitic extraction. It has a common misconception that using "ext2spice rthresh 0" will generate parasitic resistances. That is not true. The following (gzipped) script should replace the existing script (this script has not been verified and needs to be checked):

run_lvspex.sh.gz

(Attn: @d-m-bailey)

[RTimothyEdwards]

This script was mentioned and is done the correct way:

openfasoc/generators/glayout/tapeout/tapeout_and_RL/extract.bash.template

However, I do not recommend flattening the circuit for LVS extraction, as that just makes interpreting the LVS result difficult. Assuming that this is for sign-off, and the circuit has already been run through LVS during design and is assumed to be LVS clean, then it is okay to flatten the cell for sign-off LVS, although it should not be necessary.