Siliconcompiler

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**Minor:**

* Added line numbers to the error and warning log files to aid in tracking down the message in the main log.

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**Minor:**

* Fixed incorrect settings when submitting remote jobs.

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**Major:**

* Deprecated support for Python 3.6 and 3.7.

* Added ['option', 'from'], ['option', 'to'], and ['option', 'prune'] to better control the execution of the flowgraph.

* Removed leflib from SilconCompiler and use the standalone implementation provided via `pip install sc-leflib`.

**Minor:**

* Moved the built in server to use the Schema class for handling its settings.

* Fixed handling of Windows paths when submitting jobs from a Windows machine to a linux runner.

* Corrected the return behavior from the schema `.get()` to ensure lists are copied instead of being returned by reference.

* Fixed behavior where `sc-show` would require both step and index to be specified and allowed for directories to be specified as the show target.

* Tools:

* yosys: Updated to support new ABC interface for passing along dont_use cells.

* verilator: added support for assertions via ['tool', 'verilator', 'task', 'compile'/'lint', 'var', 'enable_assert']

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**Minor:**

* Added `-design` to `sc-dashboard` and ensured common behavior between `sc-show` and `sc-dashboard`.

* Disabled sorting of keys in writing of the json schema to preserve the order in the original dictionary.

* Added an alias (`siliconcompiler`) to the commandline application `sc` to allow Windows users to be better able to use SiliconCompiler.

* Tools:

* surelog: Ensure the bundled version is built using a static zlib library for Windows distribution.

* OpenROAD: Added more controls over the heatmap image generation and to only write heatmaps with data available.

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**Minor:**

* Fixes to `sc-show` for viewing remote files to ensure it does not attempt to use the file paths from the remote, but instead the local file paths.

* Tools:

* klayout: Use build technology files and layer display files in show and ensure these are placed into the outputs directory when exporting to a GDS.

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**Minor:**

* Fixes minor bug in the dashboard which prevented the launching the dashboard.

* Ensures all tool output goes through the logger.

* Improved implementation of `.valid()` to provide faster checking.

* Tools:

* OpenROAD: fixed bugs in instance creation and pin access function calls. Implemented support for multiple library corners assigned to a single scenario in timing constraints.
* yosys: Implemented support for multiple library corners assigned to a single scenario in timing constraints.