Revert "remove _XOPEN_SOURCE define as now libiouring is fixed"

This reverts commit 39e0033.

Back this out for now, seems to be causing build errors

Package.swift

@@ -73,10 +73,14 @@ let package = Package(
       name: "CIORingShims",
       dependencies: ["CIOURing"],
       cSettings: [
+        .define("_XOPEN_SOURCE=700"),
+        .define("_DEFAULT_SOURCE"),
         .define("\(cqHandlerType.rawValue)=1"),
         .unsafeFlags(["-I", SwiftLibRoot] + ASANCFlags),
       ],
       cxxSettings: [
+        .define("_XOPEN_SOURCE=700"),
+        .define("_DEFAULT_SOURCE"),
         .define("\(cqHandlerType.rawValue)=1"),
         .unsafeFlags(["-I", SwiftLibRoot] + ASANCFlags),
       ]
@@ -89,6 +93,14 @@ let package = Package(
                      .product(name: "AsyncQueue", package: "swift-async-queue"),
                      .product(name: "Logging", package: "swift-log"),
                      .product(name: "AsyncAlgorithms", package: "swift-async-algorithms")],
+      cSettings: [
+        .define("_XOPEN_SOURCE=700"),
+        .define("_DEFAULT_SOURCE"),
+      ],
+      cxxSettings: [
+        .define("_XOPEN_SOURCE=700"),
+        .define("_DEFAULT_SOURCE"),
+      ],
       swiftSettings: [
         .enableExperimentalFeature("StrictConcurrency"),
         .unsafeFlags(ASANSwiftFlags),

Sources/CIOURing/CIOURing.h

@@ -16,6 +16,11 @@
 
 #pragma once
 
+#define _XOPEN_SOURCE 700
+#ifndef _DEFAULT_SOURCE
+#define _DEFAULT_SOURCE 1
+#endif
+
 #include <linux/if_ether.h>
 #include <linux/if_packet.h>
 #include <linux/netlink.h>