forbid toggling x87 and fpregs on hard-float targets

compiler/rustc_target/src/spec/mod.rs

@@ -2603,6 +2603,18 @@ impl TargetOptions {
                 .collect();
         }
     }
+
+    pub(crate) fn has_feature(&self, search_feature: &str) -> bool {
+        self.features.split(',').any(|f| {
+            if let Some(f) = f.strip_prefix('+')
+                && f == search_feature
+            {
+                true
+            } else {
+                false
+            }
+        })
+    }
 }
 
 impl Default for TargetOptions {