build: Update docs to use only Rust and Aya

[vadorovsky]

After merging lockc-project/lockc#199 we no longer depend on llvm,
libbpf and any C-related technology, cargo and rust are enough. Because
of that simplification, it's also time to remove dapper.

Signed-off-by: Michal Rostecki [email protected]

[tacerus]

Hi!

Thank you for the docs update!

I tried to follow the new documentation, but am a bit lost - which I think is caused by my lack of understanding on how rustup toolchains work, but even after following some external documentation and online posts on cargo and rustup, I am unable to figure out:

cargo xtask build-ebpf
    Finished dev [unoptimized + debuginfo] target(s) in 0.34s
     Running `target/debug/xtask build-ebpf`
error: no such subcommand: `+nightly`
thread 'main' panicked at 'assertion failed: status.success()', xtask/src/build_ebpf.rs:62:5
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

Which cargo binary is expected in $PATH ? An online question on this issue suggested that ~/.cargo/bin is expected in order for the +nightly toolchain switching to work - however, after installing cargo using rustup install <toolchain> there is no cargo binary in ~/.cargo/bin - I only locate cargo binaries in ~/.rustup/toolchains/<toolchain>/bin, where <toolchain> is either of:

$ rustup toolchain list
stable-x86_64-unknown-linux-gnu (default)
nightly-x86_64-unknown-linux-gnu (override)

$ ls ~/.rustup/toolchains/
nightly-x86_64-unknown-linux-gnu/  stable-x86_64-unknown-linux-gnu/

I removed the system's cargo installation and I tried to set both rustup toolchain bin directories, first the stable one, then the nightly one, in $PATH, but neither of the cargo's will let me proceed.

I too tried to set either one as rustup default <toolchain>, but again, both return the same result.

Any ideas would be appreciated!

My build environment is openSUSE Leap 15.3 with rustup 1.24.3.