Temporarily ignore cargo_test_doctest_xcompile_ignores (#15348)

This was broken due to a change in
rust-lang/rust#138535. There is an approved PR
in rust-lang/rust#138877 to fix it, but it may
take a day or two for it to make its way to nightly. This should be
reverted after it hits nightly.

Author: weihanglo

tests/testsuite/test.rs

@@ -4740,7 +4740,9 @@ fn test_dep_with_dev() {
         .run();
 }
 
-#[cargo_test(nightly, reason = "-Zdoctest-xcompile is unstable")]
+// #[cargo_test(nightly, reason = "-Zdoctest-xcompile is unstable")]
+#[cargo_test]
+#[ignore = "waiting for https://github.com/rust-lang/rust/pull/138877"]
 fn cargo_test_doctest_xcompile_ignores() {
     // -Zdoctest-xcompile also enables --enable-per-target-ignores which
     // allows the ignore-TARGET syntax.