chase: Use openat2() if available

Let's make use of openat2() if we can in chaseat().

src/libc/fcntl.c

@@ -0,0 +1,11 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <fcntl.h>
+#include <sys/syscall.h>
+#include <unistd.h>
+
+#if !HAVE_OPENAT2
+int missing_openat2(int dfd, const char *filename, const struct open_how *how, size_t usize) {
+        return syscall(__NR_openat2, dfd, filename, how, usize);
+}
+#endif

src/libc/meson.build

@@ -2,6 +2,7 @@
 
 libc_wrapper_sources = files(
         'bpf.c',
+        'fcntl.c',
         'ioprio.c',
         'kcmp.c',
         'kexec.c',