Add GENERATE_PARSER_OUTPUT_DIR argument to yarp_prepare_plugin function

[traversaro]

This parameter can be used to (optionally) generate the files related to device param parser in an arbitrary location. This is typically used to generate the files in the build directory instead of the source one, removing the need of committing generate files in the repo, avoiding problems such as the one discussed in icub-tech-iit/ergocub-software#310 and #3225 (comment) .

The change is completely backward compatible, and an example of its use can be found in traversaro/ergocub-software@d811e32, from which this snippet is extracted:

yarp_prepare_plugin(couplingXCubHandMk5
                    CATEGORY device
                    TYPE CouplingXCubHandMk5
                    INCLUDE CouplingXCubHandMk5.h
                    GENERATE_PARSER
                    GENERATE_PARSER_OUTPUT_DIR ${CMAKE_CURRENT_BINARY_DIR}
                    DEFAULT ON)

if(ENABLE_couplingXCubHandMk5)
  yarp_add_plugin(yarp_couplingXCubHandMk5)

  if(MSVC)
    add_definitions(-D_USE_MATH_DEFINES)
  endif()

  target_sources(yarp_couplingXCubHandMk5 PRIVATE CouplingXCubHandMk5.cpp
                                                  CouplingXCubHandMk5.h
                                                  CouplingXCubHandMk5_ParamsParser.cpp
                                                  CouplingXCubHandMk5_ParamsParser.h)
                                                  ${CMAKE_CURRENT_BINARY_DIR}/CouplingXCubHandMk5_ParamsParser.cpp
                                                  ${CMAKE_CURRENT_BINARY_DIR}/CouplingXCubHandMk5_ParamsParser.h)

  target_include_directories(yarp_couplingXCubHandMk5 PRIVATE ${CMAKE_CURRENT_BINARY_DIR})

I am aware that there is currently a PR freeze (see #3227 (comment)), but I preferred to open a PR before I moved to work on something else, to avoid forgetting about it, so that the PR will be ready once the PR will be accepted again.

fyi @pattacini @Nicogene @PeterBowman @MSECode

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[PeterBowman]

While I like this idea, I have also realized that those .h and .cpp files will (still) be regenerated on every CMake run, thus updating the generation timestamp in the header, thus forcing recompilation of all devices that use this mechanism. Would it be possible to only regenerate/compile them when changes are applied to the .md file?

Edit: since I am implementing icub-tech-iit/ergocub-software#310 as a workaround for YARP 3.12, I forgot that (in the usual scenario) generation would be enabled explicitly via setting ALLOW_DEVICE_PARAM_PARSER_GENERATION to ON, that is, only when we want to force regeneration of said files. Please ignore my previous question.