Skip preadv2/pwritev2 for Android

Android tests run against API level 28, preadv2 and pwritev2 were
introduced in API level 33.

Author: Elie-Kh

libc-test/build.rs

@@ -2205,6 +2205,9 @@ fn test_android(target: &str) {
             // Added in API level 30, but tests use level 28.
             "memfd_create" | "mlock2" | "renameat2" | "statx" | "statx_timestamp" => true,
 
+            // Added in API level 33, but tests use level 28.
+            "preadv2" | "pwritev2" => true,
+
             // Added in glibc 2.25.
             "getentropy" => true,