genrb --omitCollationRules builds collation data and then drops the rule strings. Tests should pass with that with only warnings when the appropriate test flag is set.
Steven suggests to have a central test for whether any rule strings are available, and not even attempting related tests when no rule strings are there.
Best done after the collv2 code is merged in, which makes fewer Collator APIs depend on rule strings.
I added a patch that makes the tests pass if -w is specified, which turns certain errors into warnings. Tested with `INTLTEST_OPTS=-w CINTLTST_OPTS=-w make -j5 check`.
I built `$(COLBLDDIR)/%.res` with genrb option `--omitCollationRules`. I also removed the big5han and gb2312han tailorings. (They are not really useful sort orders but take up 192kB even without the rule strings.)
It would be nice to add testing with `--omitCollationRules` to our release tasks.
Fixed for ICU4C. I did not attempt to make these changes for ICU4J.