* [ffmpeg] Block "tensorflow" for the "all" feature on non-x64.
In https://github.com/microsoft/vcpkg/pull/21980/ , we removed all the blocks for tensorflow which were merely replicating that upstream's "supports" expression. That is the correct behavior: if upstream adds support for a thing, it should start being tested downstream. However, the "all" and "all-nonfree" features of ffmpeg attempt to turn on what is really "all supported" rather than "all", so the feature-dependency needs to be guarded.
Note that the ffmpeg[tensorflow] feature remains unguarded! It is ffmpeg[all]'s *dependency* on ffmpeg[tensorflow] that is guarded.
* Also guard ass, tensorflow, and fontconfig for uwp
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