Arch Linux build is broken

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quick-lint-js-test-lex-unicode is failing.

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e.g. https://github.com/quick-lint/quick-lint-js/runs/4309434006?check_suite_focus=true

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This is caused by version 70 of the icu library. It added support for Unicode 14, which changed data for some symbols.

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Despite having version 70 of icu, Arch Linux' Python and Go still have Unicode 13 tables.

I guess we gotta rewrite tools/generate-lex-unicode in C++ to take advantage of icu. Alternatively, we could parse Unicode tables ourselves. I think esbuild's script parses Unicode tables. EDIT: Nevermind; it uses a library which pre-parsed Unicode tables.

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Idea A: disable the lex-unicode tests entirely or unless Unicode 13 tables are in use

Idea B: use Unicode 14 tables; require Unicode 14 in lex-unicode tests

Idea C: use Unicode 14 tables; adjust lex-unicode tests to allow false positives compared to installed icu (risky)

Idea D: use union of Unicode 3, 13, 14, etc. tables (support as many standards as possible; allow false negative diagnostics for certain JS versions); adjust lex-unicode tests to allow false positives compared to installed icu (risky)

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Build fixed by implementing idea B in commit c506297.