C API header files are not installed

Issue overview

When the C library is installed, the API header files are not copied in the installation directory. Therefore clients linking against energyplus miss fundamental include files to use the library.

The relevant code is in src/EnergyPlus/CMakeLists.txt:

if(NOT BUILD_STATIC_ENERGYPLUS_API)
  install(
    TARGETS energyplusapi energyplus
    EXPORT energyplus
    RUNTIME DESTINATION ./
    LIBRARY DESTINATION ./
    ARCHIVE DESTINATION ./
    INCLUDES DESTINATION include
                         include/EnergyPlus/api
  )

  include(CMakePackageConfigHelpers)
  write_basic_package_version_file(
    "${PROJECT_BINARY_DIR}/energyplusConfigVersion.cmake"
    VERSION ${ENERGYPLUS_VERSION}
    COMPATIBILITY AnyNewerVersion
  )

  export(
    EXPORT
    energyplus
         NAMESPACE "energyplus::"
         FILE "${PROJECT_BINARY_DIR}/energyplusConfig.cmake"
  )

  install(
    EXPORT energyplus
          DESTINATION lib/cmake/energyplus
          NAMESPACE "energyplus::"
          COMPONENT "CPPAPI"
    FILE energyplusConfig.cmake
  )

  install(
    FILES
      "${PROJECT_BINARY_DIR}/energyplusConfigVersion.cmake"
    DESTINATION
      lib/cmake/energyplus/
    COMPONENT "CPPAPI"
  )
endif()

This installs the library and the cmake configuration file used to import it from other projects, but it doesn't copy the API header files.

Details

Some additional details for this issue (if relevant):

Platform (Windows 11, 22H2)
Version of EnergyPlus (23.1.0)

Checklist

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[x] Pull request created (the pull request will have additional tasks related to reviewing changes that fix this defect)

NREL / EnergyPlus