chore(tests): bpf-rs & bpf-feature tests as sudo

bpf-rs & bpf-feature tests need capabilities (to read certain directories
or load bpf programs) that are not available to a regular user.

This is strictly possible by just wrapping `cargo test` with `sudo` (such
as with `sudo -E "PATH=$PATH" $(which cargo) test --all-features`) but the
issue here (besides ergonomics) is when cargo tests build & write new
files they are now owned by root (making future non-sudo builds fail). It
might be possible to configure sudo to strictly write new files as a
separate user from root but I haven't seen that.

Ideally, we just run the created test bins with sudo after compilation and
this is possible with specifying a runner in .cargo/config.toml. We can
specify this at the workspace level for the relevant target triple but the
issue with this is that sudo disallows certain libraries to be dynamically
linked which the proc_macro crate (used transitively by bpf-rs-macros) needs.
So we're left with the option of forcing sudo to allow loading of these
libraries or to only using sudo on the crate tests that need it.

The problem is that cargo itself changes LD_LIBRARY_PATH: https://doc.rust-lang.org/cargo/reference/environment-variables.html#dynamic-library-paths
which we don't have access to from the runner's perspective, especially
given that variable shell expansion is not supported: rust-lang/cargo#10789

For now, we're choosing the latter (only using sudo on specific crates)
but we ran into another issue: config.toml is ignored on a per-crate basis when running
cargo test from a workspace. To workaround this, we change our local task
`just test` to cd into each crate and run tests from there. This is not
ideal but gets the job done for now.

We keep our github actions to just run all the tests as the original sudo
cmd for now since we don't care about the owners of the new files after
the vm disappears.

Related to #7

Signed-off-by: Milan <[email protected]>

bpf-feature/.cargo/config.toml

@@ -0,0 +1,2 @@
+[target.x86_64-unknown-linux-gnu]
+runner = "sudo -E"

bpf-rs/.cargo/config.toml

@@ -0,0 +1,2 @@
+[target.x86_64-unknown-linux-gnu]
+runner = "sudo -E"

justfile

@@ -2,10 +2,9 @@ default:
     @just --list
 
 test:
-    cargo test --all-features
-
-sudo-test:
-    sudo -E "PATH=$PATH" $(which cargo) t --all-features
+    cd ./bpf-rs && cargo test --all-features
+    cd ./bpf-feature && cargo test --all-features
+    cd ./bpf-rs-macros && cargo test --all-features
 
 build-example example:
     cargo build --all-features --example {{example}}
@@ -14,7 +13,7 @@ run example:
     just build-example {{example}}
     ./target/debug/examples/{{example}}
 
-sudorun example:
+sudo-run example:
     just build-example {{example}}
     sudo ./target/debug/examples/{{example}}