cpdup - Add another way to prevent host:path misintepretation

* Allow a local file or directory name to be prefixed with localhost:
  to prevent colons in the filename from being misinterpreted as a
  remote-host specification.

  This is in addition to the nominal absolute-path method to prevent
  misinterpretation (a '/' occuring before any ':' prevents
  misinterpretation of the ':' as a remote-host specification)
Added CFLAGS+= -DTARGET_SYSTEM_ROOT=\"${USRDATA_PREFIX}\" to makefile for ld.

The ld that is build into ctools_x86_64 to build world tries to check runtime
dynamic dependencies. For this it tried loading /var/run/ld-elf.so.hints and
hence failed if symbols in libc or libpthread are removed for the new
buildworld.