message: cmake: fix version in incremental build
  This fixes the version which was not correctly updated in an incremental
  build. The reason was that configure_file is only run when cmake is
  doing the initial configuration, and not in later incremental builds.
  Therefore, the cmake configure_file templating is replaced with just
  sed.
diff: @@ -67,7 +67,13 @@ set_target_properties(dronecode_sdk
  PROPERTIES COMPILE_FLAGS ${warnings}
  )
  -configure_file(version.h.in ${CMAKE_CURRENT_BINARY_DIR}/version.h)
  +add_custom_command(
  + TARGET dronecode_sdk
  + COMMAND sed "s/@VERSION_STR@/${VERSION_STR}/" ${PROJECT_SOURCE_DIR}/core/version.h.in > ${CMAKE_CURRENT_BINARY_DIR}/version.h
  + PRE_BUILD
  + DEPENDS ${PROJECT_SOURCE_DIR}/version
  +)
  +
  target_include_directories(dronecode_sdk PRIVATE ${CMAKE_CURRENT_BINARY_DIR})
  install(TARGETS dronecode_sdk
  