See db236e588d "steam: Do $PATH lookup in steam.desktop [...]".
tl;dr: Otherwise widget/panel/desktop icons in DEs like KDE break.
Simply stop adding the full derivation path for neovim and stick with
how upstream uses no path at all.
While here, take care of gnvim.desktop as well by adjusting the sed(1)
expression (and simplifying it in one go); I do not use gnvim.desktop
but built it and confirmed the resulting files to contain no full paths
any longer.
When running the default builder for Rust, the artifacts would be stored
in `target/<arch>/<profile>`, however the `install`-target expects the
default structure (`target/<profile>`) of `cargo`-builds.
When using the Makefile for building as well, the expected structure is
created instead.
Changes the default fetcher in the Rust Platform to be the newer
`fetchCargoTarball`, and changes every application using the current default to
instead opt out.
This commit does not change any hashes or cause any rebuilds. Once integrated,
we will start deleting the opt-outs and recomputing hashes.
See #79975 for details.
