If the post subset cmap12 table is equivalent to another cmap subtable don't include the 12 table in the final subset. Matches change https://github.com/fonttools/fonttools/pull/2146 from fontTools.
Speed-up subset tests by saving TTX dump of expected output instead of
generating it each time the tests are run.
Cuts down meson test --suite=subset on my system from:
real 0m38.977s
user 1m12.024s
sys 0m10.547s
to:
real 0m22.291s
user 0m44.548s
sys 0m9.221s
Part of https://github.com/harfbuzz/harfbuzz/issues/3089
Qunxin Liu
Garret Rieger
Khaled Hosny