message: cmake: disallow in-source builds
diff: #
  # ----------------------------------------------------------------------------
  +# Disable in-source builds to prevent source tree corruption.
  +if(" ${CMAKE_SOURCE_DIR}" STREQUAL " ${CMAKE_BINARY_DIR}")
  + message(FATAL_ERROR "
  +FATAL: In-source builds are not allowed.
  + You should create separate directory for build files.
  +")
  +endif()
  include(cmake/OpenCVMinDepVersions.cmake)
  @@ -1386,13 +1393,6 @@ status("")
  ocv_finalize_status()
  -# ----------------------------------------------------------------------------
  -# Warn in the case of in-source build
  -# ----------------------------------------------------------------------------
  -if("${CMAKE_CURRENT_SOURCE_DIR}" STREQUAL "${CMAKE_CURRENT_BINARY_DIR}")
  - message(WARNING "The source directory is the same as binary directory. \"make clean\" may damage the source tree")
  -endif()
  -
  # ----------------------------------------------------------------------------
  # CPack stuff
  # ----------------------------------------------------------------------------
  