Include the bits/syscalls.h header

Author: gnzlbg

libc-test/build.rs

@@ -2263,6 +2263,7 @@ fn test_linux(target: &str) {
     cfg.flag("-Wno-deprecated-declarations");
 
     headers! { cfg:
+               "bits/syscall.h",
                "ctype.h",
                "dirent.h",
                "dlfcn.h",