bpf: fix some clippy warnings

bpf/aya-bpf-bindings/build.rs

@@ -1,9 +1,9 @@
 use std::env;
 
 fn main() {
-    if !env::var("CARGO_CFG_BPF_TARGET_ARCH").is_ok() {
+    if env::var("CARGO_CFG_BPF_TARGET_ARCH").is_err() {
         let arch = env::var("HOST").unwrap();
-        let arch = arch.splitn(2, "-").next().unwrap();
+        let arch = arch.splitn(2, '-').next().unwrap();
         println!("cargo:rustc-cfg=bpf_target_arch=\"{}\"", arch);
     }
 }

bpf/aya-bpf-cty/build.rs

@@ -1,9 +1,9 @@
 use std::env;
 
 fn main() {
-    if !env::var("CARGO_CFG_BPF_TARGET_ARCH").is_ok() {
+    if env::var("CARGO_CFG_BPF_TARGET_ARCH").is_err() {
         let arch = env::var("HOST").unwrap();
-        let arch = arch.splitn(2, "-").next().unwrap();
+        let arch = arch.splitn(2, '-').next().unwrap();
         println!("cargo:rustc-cfg=bpf_target_arch=\"{}\"", arch);
     }
 }

bpf/aya-bpf-macros/src/expand.rs

@@ -226,8 +226,8 @@ impl CgroupSkb {
 
         Ok(CgroupSkb {
             item,
-            name,
             expected_attach_type,
+            name,
         })
     }
 
@@ -260,7 +260,7 @@ fn pop_arg(args: &mut Args, name: &str) -> Option<String> {
 }
 
 fn err_on_unknown_args(args: &Args) -> Result<()> {
-    for arg in &args.args {
+    if let Some(arg) = args.args.get(0) {
         return Err(Error::new_spanned(&arg.name, "invalid argument"));
     }
 

bpf/aya-bpf/src/programs/sk_skb.rs

@@ -36,7 +36,7 @@ impl SkSkbContext {
     }
 
     #[inline]
-    pub fn cb_mut(&self) -> &mut [u32] {
+    pub fn cb_mut(&mut self) -> &mut [u32] {
         unsafe { &mut (*self.skb).cb }
     }