Well, that sort of helped. Actually the referenced XDC User's Guide might have been more relevant: http://rtsc.eclipse.org/docs-tip/XDCtools_User's_Guide
What I came up with less than a clean solution, but better than nothing. I have added the following lines to package.bld:
Pkg.makePrologue = "\nEXAMPLES_ROOTDIR := /home/[me]/ti-dvsdk_dm3730-evm_04_03_00_06/code/ce\ninclude $(EXAMPLES_ROOTDIR)/xdcpaths.mak\nXDC_PATH := $(EXAMPLES_ROOTDIR);$(XDC_PATH)"; Pkg.makeEpilogue = "\ninstall:\n\t@tar xvf my_servers_all_codecs.tar -C /exports/rootfs/opt\n\t@echo\n\t@echo Installed binaries..";
It's not a great solution because it has to be done separately for the codec server and the app, and isn't very smart about where it puts files, but it's better than nothing.