Fix problems when building the whole tree for multiple HDL targets which use the same tools
-- e.g. when both ml605 and zed are in the list being built

tools/cdk/include/hdl/hdl-assembly.mk: properly avoid excluded targets
tools/cdk/include/hdl/hdl-make.mk: avoid collisions between different targets using the same tool set
-- also add a separate module for target preprocessing that can be used separate from hdl-pre.mk
tools/cdk/include/hdl/hdl-platform.mk: adjust for multi-target-same-tool fixes
tools/cdk/include/hdl/hdl-worker.mk: ditto
tools/cdk/include/hdl/quartus.mk: ditto
tools/cdk/include/hdl/xst.mk: ditto
tools/cdk/include/hdl/hdl-pre.mk: use new (extracted) target preprocessing module
tools/cdk/include/lib.mk: use the new target preprocessing module and avoid the inappropriate hdl-pre.mk