build(signal_processing): add Boost to build_export_depend

[esteve]

Description

This makes sure that downstream packages have the correct dependencies (e.g. they can include boost/optional.hpp)

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[codecov]

Codecov Report

Base: 11.79% // Head: 11.79% // Increases project coverage by +0.00% 🎉

Coverage data is based on head (551a9ba) compared to base (ce82f3d).
Patch has no changes to coverable lines.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2917   +/-   ##
=======================================
  Coverage   11.79%   11.79%           
=======================================
  Files        1322     1322           
  Lines       92804    92789   -15     
  Branches    25004    24996    -8     
=======================================
  Hits        10944    10944           
+ Misses      70386    70371   -15     
  Partials    11474    11474           

Flag	Coverage Δ		*Carryforward flag
differential	3.47% <ø> (?)
total	11.79% <ø> (+<0.01%)	⬆️	Carriedforward from ce82f3d

*This pull request uses carry forward flags. Click here to find out more.

Impacted Files	Coverage Δ
...havior_path_planner/behavior_path_planner_node.hpp	0.00% <ø> (ø)
...ner/include/behavior_path_planner/data_manager.hpp	0.00% <ø> (ø)
...lanner/scene_module/avoidance/avoidance_module.hpp	0.00% <ø> (ø)
...th_planner/scene_module/scene_module_interface.hpp	0.00% <ø> (ø)
...or_path_planner/src/behavior_path_planner_node.cpp	0.15% <ø> (+<0.01%)	⬆️
...er/src/scene_module/avoidance/avoidance_module.cpp	0.00% <ø> (ø)
...ne_module/lane_following/lane_following_module.cpp	0.00% <ø> (ø)
...er/src/scene_module/pull_over/pull_over_module.cpp	0.00% <ø> (ø)
.../src/scene_module/side_shift/side_shift_module.cpp	0.00% <ø> (ø)

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