fix(otel-process-ctx): use raw syscall for memfd_create to support old glibc

libc::memfd_create requires glibc >= 2.27, causing a link error on CentOS 7
(glibc 2.17). Use libc::syscall(SYS_memfd_create, ...) instead, which bypasses
the glibc wrapper and works with any glibc version, matching the previous rustix
behavior.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: yannham

libdd-library-config/src/otel_process_ctx.rs

@@ -340,8 +340,13 @@ pub mod linux {
 
     /// Creates a `memfd` file descriptor with the given name and flags.
     fn try_memfd(name: &CStr, flags: libc::c_uint) -> anyhow::Result<OwnedFd> {
+        // We use the raw syscall rather than `libc::memfd_create` because the latter requires
+        // glibc >= 2.27, while `syscall()` + `SYS_memfd_create` works with any glibc version.
         // Safety: name is a valid NUL-terminated string; flags are constant bit flags.
-        let fd = unsafe { libc::memfd_create(name.as_ptr(), flags) };
+        let fd = unsafe {
+            libc::syscall(libc::SYS_memfd_create, name.as_ptr(), flags as libc::c_long)
+                as libc::c_int
+        };
         check_syscall_retval(fd, "memfd_create failed")?;
         // Safety: fd is a valid file descriptor just returned by memfd_create.
         Ok(unsafe { OwnedFd::from_raw_fd(fd) })