openjdk includes solar87, solar88, solar89 files which were removed from tzdata years ago, and never really used.

"""
    The files solar87, solar88, and solar89 are no longer distributed.
    They were a negative experiment - that is, a demonstration that
    tz data can represent solar time only with some difficulty and error.
    Their presence in the distribution caused confusion, as Riyadh
    civil time was generally not solar time in those years.
"""

zone.tab is included instead of zone1970.tab even though the latter is surprisingly the newer version!

If you delete these files, everything seems to still just work!

R make/data/tzdata/solar87
R make/data/tzdata/solar88
R make/data/tzdata/solar89
R make/data/tzdata/zone.tab
R test/sun/util/calendar/zi/tzdata/solar87
R test/sun/util/calendar/zi/tzdata/solar88
R test/sun/util/calendar/zi/tzdata/solar89
R test/sun/util/calendar/zi/tzdata/zone.tab

BTW, why are there two different test versions of jdk11_backward?
./test/sun/util/calendar/zi/tzdata_jdk/jdk11_backward
./test/sun/util/calendar/zi/tzdata/jdk11_backward