`sage.plot.animate`: Use `Executable.absolute_filename`, pass configured FFMPEG via sage-conf

[beew]

Part of:

• Meta-ticket: Set environment for subprocesses invoked by Sage #30818

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Original issue description:

I have compiled sage with a local version of ffmpeg successfully by issuing these commands before running configure

export PATH="$HOME/opt/ffmpeg6/bin:$PATH"
export LD_LIBRARY_PATH="$HOME/opt/ffmpeg6/lib:$LD_LIBRARY_PATH"
export PKG_CONFIG_PATH="$HOME/opt/ffmpeg6/lib/pkgconfig:$PKG_CONFIG_PATH"

Now I would like to make sure that sage respects these environmental variables at run time. Should I put them in .sage/sagerc?

Running sage --sh, I found these two environmental variables

SAGE_ORIG_PATH

SAGE_ORIG_PATH_SET

I am trying to find some documentation on these but can't find any. Can someone explain to me what these are?

OS is Ubuntu 22.04, sage 9.8

[mkoeppe]

SAGE_ORIG_PATH is no longer in use in the runtime environment. It has a limited use during the build.

Sage does not have the mechanism that you are looking for.

If you want ffmpeg in your PATH, you will have to set PATH in your ~/.profile or ~/.bashrc etc.; or symlink it into a directory that is in PATH. Likewise with LD_LIBRARY_PATH (if setting this is actually needed).

PKG_CONFIG_PATH is not needed at runtime.