megasync: temporarily remove ffmpeg dependency

[michojel]

until patched to work with ffmpeg 4.4

See #120705 (comment)

Upstream issue: meganz/MEGAsync#578

Honestly, I haven't noticed a difference when compiled without ffmpeg.

Motivation for this change

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS linux)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Ensured that relevant documentation is up to date
• Fits CONTRIBUTING.md.

[michojel]

@lunik1 PTAL

[r-rmcgibbo]

Result of nixpkgs-review pr 123620 at b275ddd run on x86_64-linux 1

2 packages built successfully:

• megasync
• tests.trivial

15 suggestions:

• warning: stale-substitute

  Stale substituteInPlace detected.
  substituteStream(): WARNING: pattern '/bin/bash' doesn't match anything in file 'src/MEGASync/mega/bindings/ios/3rdparty/build-webrtc.sh'
  Near pkgs/applications/misc/megasync/default.nix:121:0:

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• warning: stale-substitute

  Stale substituteInPlace detected.
  substituteStream(): WARNING: pattern '/bin/bash' doesn't match anything in file 'src/MEGASync/mega/bindings/ios/3rdparty/build-all.sh'
  Near pkgs/applications/misc/megasync/default.nix:121:0:

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• warning: stale-substitute

  Stale substituteInPlace detected.
  substituteStream(): WARNING: pattern '/bin/bash' doesn't match anything in file 'src/MEGASync/mega/bindings/ios/3rdparty/build-libwebsockets.sh'
  Near pkgs/applications/misc/megasync/default.nix:121:0:

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• warning: stale-substitute

  Stale substituteInPlace detected.
  substituteStream(): WARNING: pattern '/bin/bash' doesn't match anything in file 'src/MEGASync/mega/contrib/build_ffmpeg/ffmpeg/build_minimum.sh'
  Near pkgs/applications/misc/megasync/default.nix:121:0:

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• warning: stale-substitute

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  substituteStream(): WARNING: pattern '/bin/bash' doesn't match anything in file 'src/MEGASync/mega/bindings/ios/3rdparty/build-openssl.sh'
  Near pkgs/applications/misc/megasync/default.nix:121:0:

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• warning: stale-substitute

  Stale substituteInPlace detected.
  substituteStream(): WARNING: pattern '/bin/bash' doesn't match anything in file 'src/MEGASync/mega/bindings/ios/3rdparty/build-mediainfolib.sh'
  Near pkgs/applications/misc/megasync/default.nix:121:0:

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• warning: stale-substitute

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  substituteStream(): WARNING: pattern '/bin/bash' doesn't match anything in file 'src/MEGASync/mega/autogen.sh'
  Near pkgs/applications/misc/megasync/default.nix:121:0:

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• warning: stale-substitute

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  substituteStream(): WARNING: pattern '/bin/bash' doesn't match anything in file 'src/MEGASync/mega/bindings/ios/3rdparty/build-cares.sh'
  Near pkgs/applications/misc/megasync/default.nix:121:0:

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• warning: stale-substitute

  Stale substituteInPlace detected.
  substituteStream(): WARNING: pattern '/bin/bash' doesn't match anything in file 'src/MEGASync/mega/clean.sh'
  Near pkgs/applications/misc/megasync/default.nix:121:0:

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• warning: stale-substitute

  Stale substituteInPlace detected.
  substituteStream(): WARNING: pattern '/bin/bash' doesn't match anything in file 'src/MEGASync/mega/contrib/clang-analyzer.sh'
  Near pkgs/applications/misc/megasync/default.nix:121:0:

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• warning: stale-substitute

  Stale substituteInPlace detected.
  substituteStream(): WARNING: pattern '/bin/bash' doesn't match anything in file 'src/MEGASync/mega/bindings/ios/3rdparty/build-curl.sh'
  Near pkgs/applications/misc/megasync/default.nix:121:0:

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• warning: stale-substitute

  Stale substituteInPlace detected.
  substituteStream(): WARNING: pattern '/bin/bash' doesn't match anything in file 'src/MEGASync/mega/bindings/ios/3rdparty/build-libuv.sh'
  Near pkgs/applications/misc/megasync/default.nix:121:0:

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  121 |     description =
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• warning: stale-substitute

  Stale substituteInPlace detected.
  substituteStream(): WARNING: pattern '/bin/bash' doesn't match anything in file 'src/MEGASync/mega/bindings/ios/3rdparty/build-libsodium.sh'
  Near pkgs/applications/misc/megasync/default.nix:121:0:

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  121 |     description =
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• warning: stale-substitute

  Stale substituteInPlace detected.
  substituteStream(): WARNING: pattern '/bin/bash' doesn't match anything in file 'src/MEGASync/mega/bindings/ios/3rdparty/build-cryptopp.sh'
  Near pkgs/applications/misc/megasync/default.nix:121:0:

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• warning: stale-substitute

  Stale substituteInPlace detected.
  substituteStream(): WARNING: pattern '/bin/bash' doesn't match anything in file 'src/MEGASync/mega/contrib/build_pdfium/build.sh'
  Near pkgs/applications/misc/megasync/default.nix:121:0:

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  121 |     description =
      | ^