* `ifp::initialize_floorplan`: new key `-flip_sites` allows listing sites to flip in the floorplan, i.e., use FS on even rows and N on odd rows.
* + test case
* `src/ifp/src/InitFloorplan.i`: More consistent indentation
* `default.nix`: added handy alias to format changed c/cxx files
Signed-off-by: Mohamed Gaber <donn@efabless.com>
Replacing `etc/shell.nix`, this is a [flake](https://nixos.wiki/wiki/Flakes) based on the OpenROAD Nix derivation used for OpenLane 2. With Nix installed with flakes enabled, getting an OpenROAD environment is as simple as typing `nix develop`.
Also fixes issue with versions of OpenROAD built in the dev environments failing to launch the GUI.
Signed-off-by: Mohamed Gaber <donn@efabless.com>
