Fix new dead_code instances in std_detect

Author: GrigorenkoPV

library/stdarch/crates/std_detect/src/detect/os/linux/aarch64.rs

@@ -126,8 +126,8 @@ struct AtHwcap {
     f8fma: bool,
     f8dp4: bool,
     f8dp2: bool,
-    f8e4m3: bool,
-    f8e5m2: bool,
+    // f8e4m3: bool,
+    // f8e5m2: bool,
     smelutv2: bool,
     smef8f16: bool,
     smef8f32: bool,
@@ -230,8 +230,8 @@ impl From<auxvec::AuxVec> for AtHwcap {
             f8fma: bit::test(auxv.hwcap2, 52),
             f8dp4: bit::test(auxv.hwcap2, 53),
             f8dp2: bit::test(auxv.hwcap2, 54),
-            f8e4m3: bit::test(auxv.hwcap2, 55),
-            f8e5m2: bit::test(auxv.hwcap2, 56),
+            // f8e4m3: bit::test(auxv.hwcap2, 55),
+            // f8e5m2: bit::test(auxv.hwcap2, 56),
             smelutv2: bit::test(auxv.hwcap2, 57),
             smef8f16: bit::test(auxv.hwcap2, 58),
             smef8f32: bit::test(auxv.hwcap2, 59),

library/stdarch/crates/std_detect/src/detect/os/linux/s390x.rs

@@ -10,6 +10,8 @@ pub(crate) fn detect_features() -> cache::Initializer {
     cache(opt_hwcap, facilities)
 }
 
+// FIXME(#143487): is it okay that the fields are never read?
+#[expect(dead_code)]
 #[derive(Debug, Default, PartialEq)]
 struct AtHwcap {
     esan3: bool,