Fix CHOMP motion planner build on Windows

[Ace314159]

Description

#809 broke the build on Windows because it uses a static variable, which requires manual visibility headers in order to be exported into the DLL. This PR generates the visibility header and exports the static variable, which fixes the build. Here is a successful CI build run for Foxy.

Checklist

• Required by CI: Code is auto formatted using clang-format
• Extend the tutorials / documentation reference
• Document API changes relevant to the user in the MIGRATION.md notes
• Create tests, which fail without this PR reference
• Include a screenshot if changing a GUI
• While waiting for someone to review your request, please help review another open pull request to support the maintainers

[codecov]

Codecov Report

Merging #890 (e2afd3b) into main (71738d9) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #890   +/-   ##
=======================================
  Coverage   57.90%   57.90%           
=======================================
  Files         310      310           
  Lines       26072    26072           
=======================================
  Hits        15095    15095           
  Misses      10977    10977           

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[tylerjw]

Thank you for this fix.