Better error & download url if ffmpeg is missing #14234

Job	Run time
cpp-paths-filter	6s
docs-paths-filter	7s
python-paths-filter	6s
rust-paths-filter	4s
web-paths-filter	11s
Checks / Rerun lints	27s
Checks / Lint markdown	21s
Checks / markdown-paths-filter	5s
Checks / Check if running codegen would produce any changes	54s
Checks / Spell Check	7s
Checks / Misc formatting	19s
Update PR Body / Update PR body	22s
Rust Checks / Rust lints (fmt, check, clippy, tests, doc)	8m 25s
Rust Checks / Test on macOS and Windows	0s
Checks / Check links	0s
C++ tests	0s
Python Checks	0s
Deploy Landing Preview	0s
Minimum CLI Build / Set Config (linux-x64)	2s
Build rerun_js / Build rerun_js	2m 59s
Build web viewer / Build web viewer	3m 9s
Minimum CLI Build / Build rerun-cli (ubuntu-latest-16-cores)	5m 11s
Upload Web / Upload web build to google cloud (wasm32 + wasm-bindgen)	10s
Save PR Summary / Create HTML summary for PR	37s
Minimum Wheel Build / Set Config (linux-x64)	4s
Minimum Wheel Build / Build Wheels (ubuntu-latest-16-cores)	2m 8s
Minimum Wheel Test / Set Config (linux-x64)	2s
Minimum Wheel Test / Test Wheels (ubuntu-latest-16-cores)	3m 48s
	29m 44s

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