What's the "preprocessed" image.c? In any case, here's that part of image.c after reverted all local changes to it so that it's the exact same as on master:

  /* Suppress GCC deprecation warnings starting in librsvg 2.45.1 for
     rsvg_handle_write and rsvg_handle_close.  FIXME: Use functions
     like rsvg_handle_new_from_gfile_sync on newer librsvg versions,
     and remove this hack.  */
  #if GNUC_PREREQ (4, 6, 0)
   #pragma GCC diagnostic push
  #endif
  #if LIBRSVG_CHECK_VERSION (2, 45, 1) && GNUC_PREREQ (4, 2, 0)
   #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
  #endif

PS: I was able to build emacs locally after commenting out the " #if LIBRSVG_CHECK_VERSION .. #endif" portion.