Skip uc_sigmask64 on skip_field

Author: JohnTitor

libc-test/build.rs

@@ -1410,8 +1410,6 @@ fn test_android(target: &str) {
             // These are tested as part of the linux_fcntl tests since there are
             // header conflicts when including them with all the other structs.
             "termios2" => true,
-            // uc_sigmask and uc_sigmask64 of ucontext_t are an anonymous union
-            "ucontext_t" => true,
 
             _ => false,
         }
@@ -1478,7 +1476,9 @@ fn test_android(target: &str) {
         // signalfd had SIGSYS fields added in Android 4.19, but CI does not have that version yet.
         (struct_ == "signalfd_siginfo" && (field == "ssi_syscall" ||
                                            field == "ssi_call_addr" ||
-                                           field == "ssi_arch"))
+                                           field == "ssi_arch")) ||
+        // uc_sigmask and uc_sigmask64 of ucontext_t are an anonymous union
+        (struct_ == "ucontext_t" && field == "uc_sigmask__c_anonymous_union")
     });
 
     cfg.generate("../src/lib.rs", "main.rs");