In the build Makefiles, this adds a function (uniq) which removes duplicate entries from lists. We apply this to the DESIGN_SRCS passed to the Vivado build process. This eliminates some warnings from duplicate source files caused by redundantly referencing source files in the Makefiles, possibly because they are listed in more than one source file variable. Original-commit: 1944263412d329d53b32a17e9735b79e59e319d7