message: Fix in-source cmake build.
  When doing sequence "cmake .; make; cmake ." the second cmake failed
  because targets translation_foo and po_foo were defined twice (where foo
  is some module). One of those targets came from foo.cpp, but another one
  from foo.so, because we use GLOB to gather list of modules.
diff: @@ -90,8 +90,6 @@ foreach(modpath ${all_modules})
  continue()
  endif()
  - list(APPEND actual_modules "${modpath}")
  -
  set(modenabled true)
  if(moddisable_${mod})
  @@ -109,14 +107,16 @@ foreach(modpath ${all_modules})
  if(modenabled)
  if(modtype STREQUAL "cpp")
  add_cxx_module("${mod}" "${modpath}")
  - endif()
  - if(modtype STREQUAL "pm")
  + elseif(modtype STREQUAL "pm")
  add_perl_module("${mod}" "${modpath}")
  - endif()
  - if(modtype STREQUAL "py")
  + elseif(modtype STREQUAL "py")
  add_python_module("${mod}" "${modpath}")
  + else()
  + continue()
  endif()
  endif()
  +
  + list(APPEND actual_modules "${modpath}")
  endforeach()
  if(HAVE_I18N)
  