Fix building Docker image with local dependencies

[eszpotanski]

When local dependencies are prepared with setup.sh script, dependencies/ folder is created, which is automatically copied into Docker image and sourced by dev_env.sh. This results in missing SWIG error:

$ sudo setup.sh
[...]
$ ./build_openroad --latest
[...]
> [4/4] RUN ./build_openroad.sh --no_init --local --threads 16:
139.8   "4.0")
139.8 Call Stack (most recent call first):
139.8   /OpenROAD-flow-scripts/dependencies/share/cmake-3.24/Modules/FindPackageHandleStandardArgs.cmake:594 (_FPHSA_FAILURE_MESSAGE)
139.8   /OpenROAD-flow-scripts/dependencies/share/cmake-3.24/Modules/FindSWIG.cmake:153 (find_package_handle_standard_args)
139.8   src/CMakeLists.txt:169 (find_package)
139.8
139.8
139.8 -- Configuring incomplete, errors occurred!
139.8 See also "/OpenROAD-flow-scripts/tools/OpenROAD/build/CMakeFiles/CMakeOutput.log".
139.8 See also "/OpenROAD-flow-scripts/tools/OpenROAD/build/CMakeFiles/CMakeError.log".
------
Dockerfile.builder:16
--------------------
  14 |     RUN cat tools/yosys/Makefile | grep ABCREV
  15 |     RUN cd tools/yosys/abc; git status; cd -
  16 | >>> RUN ./build_openroad.sh --no_init --local --threads ${numThreads}
  17 |
--------------------
ERROR: failed to solve: process "/bin/sh -c ./build_openroad.sh --no_init --local --threads ${numThreads}" did not complete successfully: exit code: 1

This PR fixes it by ignoring dependencies/ directory during Docker build.

[oharboe]

@eszpotanski Missing 'y' is a driveby fix, no? Should be in separate PR. fix and force push this one to make it single concern?

[oharboe]

@eszpotanski Accidentally mentioned Matt above. Fixed.

[eszpotanski]

Done, missing -y has separate PR https://github.com/The-OpenROAD-Project/OpenROAD-flow-scripts/pull/2016

[oharboe]

@maliberty LGTM