test: linux: Unskip statx and statx_timestamp tests

The mentioned issues with `#include` no longer seem to happen, so start
testing these again.

(backport <#4760>)
(cherry picked from commit 758dc77)

Author: tgross35

libc-test/build.rs

@@ -4138,12 +4138,6 @@ fn test_linux(target: &str) {
             // glibcs (see https://github.com/rust-lang/libc/issues/1410)
             "ucontext_t" if gnu => true,
 
-            // FIXME(linux): Somehow we cannot include headers correctly in glibc 2.30.
-            // So let's ignore for now and re-visit later.
-            // Probably related: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91085
-            "statx" => true,
-            "statx_timestamp" => true,
-
             // On Linux, the type of `ut_exit` field of struct `utmpx`
             // can be an anonymous struct, so an extra struct,
             // which is absent in musl, has to be defined.