[Merge][CMake] -r7383 from branches/cmake: Prevent generation of pdf even if one uses safepdf

Previously there still was a dependency to build the pdf which miserably failed as we don not distribute tex files.

[[Imported from SVN: r7400]]

cmake/modules/DuneDoc.cmake

@@ -57,14 +57,15 @@ MACRO(create_doc_install filename targetdir)
   find_file(_src_file ${targetfile} ${CMAKE_CURRENT_SOURCE_DIR})
   if(NOT _src_file)
     set(_src_file ${filename})
+    set(_need_to_generate TRUE)
   endif(NOT _src_file)
   set(install_command ${CMAKE_COMMAND} -D FILES=${_src_file} -D DIR=${CMAKE_INSTALL_PREFIX}/${targetdir} -P ${SCRIPT_DIR}/InstallFile.cmake)
   # create a custom target for the installation
-  if("${ARGC}" EQUAL "3")
+  if("${ARGC}" EQUAL "3" AND _need_to_generate)
     set(_depends ${ARGV2})
-  else("${ARGC}" EQUAL "3")
-    set(_depends  ${filename})
-  endif("${ARGC}" EQUAL "3")
+  else("${ARGC}" EQUAL "3" AND _need_to_generate)
+    set(_depends  ${_src_file})
+  endif("${ARGC}" EQUAL "3" AND _need_to_generate)
   add_custom_target(install_${targetfile} ${install_command}
     COMMENT "Installing ${filename} to ${targetdir}"
     DEPENDS ${_depends})