Add Sourcegraph CLI package.

[dlorenc]

There's still an issue with the ldflags variable for the version not working.

Fixes:

Related:

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For new package PRs only

• This PR is marked as fixing a pre-existing package request bug
  • Alternatively, the PR is marked as related to a pre-existing package request bug, such as a dependency
• REQUIRED - The package is available under an OSI-approved or FSF-approved license
• REQUIRED - The version of the package is still receiving security updates
• REQUIRED - The package is added to packages.txt

[dlorenc]

Hi live stream! We still have to fix the ldflag here.