netlist: gate netlist filegroup use-case

[oharboe]

The intention here is to document the gate netlist file group use-case.

It needs work... fails:

$ bazel build lb_32x128_final
INFO: Analyzed target //:lb_32x128_final (1 packages loaded, 1652 targets configured).
INFO: Found 1 target...
Target //:lb_32x128_final up-to-date:
  bazel-bin/results/asap7/lb_32x128/base/6_final.gds
  bazel-bin/results/asap7/lb_32x128/base/6_final.odb
  bazel-bin/results/asap7/lb_32x128/base/6_final.sdc
  bazel-bin/results/asap7/lb_32x128/base/6_final.spef
  bazel-bin/results/asap7/lb_32x128/base/6_final.v
  bazel-bin/reports/asap7/lb_32x128/base/6_finish.rpt
  bazel-bin/reports/asap7/lb_32x128/base/VDD.rpt
  bazel-bin/reports/asap7/lb_32x128/base/VSS.rpt
INFO: Elapsed time: 0.374s, Critical Path: 0.02s
INFO: 1 process: 1 internal.
INFO: Build completed successfully, 1 total action
$ bazel build gatelist
INFO: Analyzed target //:gatelist (1 packages loaded, 2 targets configured).
ERROR: /home/oyvind/bazel-orfs/BUILD:368:10: //:gatelist: missing input file '//:results/asap7/lb_32x128/base/6_final.v'
ERROR: /home/oyvind/bazel-orfs/BUILD:368:10: 1 input file(s) do not exist
Target //:gatelist failed to build
Use --verbose_failures to see the command lines of failed build steps.
INFO: Elapsed time: 0.088s, Critical Path: 0.00s
INFO: 1 process: 1 internal.
ERROR: Build did NOT complete successfully