message: Fix CMake generated Xcode project dependency issue
diff: @@ -213,10 +213,23 @@ elseif(ANDROID)
  list(APPEND REALM_EXTRA_LIBS atomic)
  endif()
  +set(REALM_XCODE_DEPENDENCY "")
  +if(CMAKE_GENERATOR STREQUAL Xcode)
  # The placeholder file is needed in order to make builds work on Xcode
  # The issue is described in the last sentence here:
  # https://cmake.org/cmake/help/v3.7/command/add_library.html#object-libraries
  -add_library(realm STATIC $<TARGET_OBJECTS:realm-objects> placeholder.cpp)
  + # Another problem is that Xcode does not see changes in the realm-objects
  + # target, to solve this we trigger rebuiliding the library by making
  + # placeholder.cpp depend on all the sources rather than realm-objects.
  + set(REALM_XCODE_DEPENDENCY "placeholder.cpp")
  + add_custom_command(
  + OUTPUT ${REALM_XCODE_DEPENDENCY}
  + DEPENDS ${REALM_SOURCES} ${REALM_INSTALL_ALL_HEADERS}
  + COMMAND echo \"extern int xcode_unused\; //This file is generated by CMake for Xcode builds\" > ${REALM_XCODE_DEPENDENCY}
  + )
  +endif()
  +
  +add_library(realm STATIC $<TARGET_OBJECTS:realm-objects> ${REALM_XCODE_DEPENDENCY})
  target_link_libraries(
  realm
  @@ -229,7 +242,7 @@ if(ANDROID OR CMAKE_SYSTEM_NAME MATCHES "^Windows")
  endif()
  if(NOT REALM_SKIP_SHARED_LIB)
  - add_library(realm-shared SHARED $<TARGET_OBJECTS:realm-objects> placeholder.cpp)
  + add_library(realm-shared SHARED $<TARGET_OBJECTS:realm-objects> ${REALM_XCODE_DEPENDENCY})
  set_target_properties(
  realm-shared PROPERTIES
  