This restriction was added to fix#7373 back then, which was a symbol conflict
between FreeType's bundled copy of gzip/zlib, and distro packages.
But we also unbundled FreeType's zlib in #69395 so this is no longer an issue.
On the other hand recent issues pointed out that using system-provided icu4c
or harfbuzz can cause issues (#91401, #100301). We still allow it for now but
raise a warning.
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