Guard out extended or fs attributes related code on WASI

This commit guards out the extended attributes and file system
attributes related code on WASI as WASI does not support these
features. Just return nothing or ignore the set request.

Author: kateinoigakukun

Sources/FoundationEssentials/FileManager/FileManager+Files.swift

@@ -484,7 +484,13 @@ extension _FileManagerImpl {
 #endif
     }
 
-#if !os(Windows)
+#if os(Windows)
+#elseif os(WASI)
+    private func _extendedAttributes(at path: UnsafePointer<CChar>, followSymlinks: Bool) throws -> [String : Data]? {
+        // WASI does not support extended attributes
+        return nil
+    }
+#else
     private func _extendedAttribute(_ key: UnsafePointer<CChar>, at path: UnsafePointer<CChar>, followSymlinks: Bool) throws -> Data? {
         #if canImport(Darwin)
         var size = getxattr(path, key, nil, 0, 0, followSymlinks ? 0 : XATTR_NOFOLLOW)
@@ -693,6 +699,9 @@ extension _FileManagerImpl {
                 ]
             }
         }
+#elseif os(WASI)
+        // WASI does not support file system attributes
+        return [:]
 #else
         try fileManager.withFileSystemRepresentation(for: path) { rep in
             guard let rep else {

Sources/FoundationEssentials/FileManager/FileManager+Utilities.swift

@@ -173,7 +173,12 @@ extension _FileManagerImpl {
         #endif
     }
 
-#if !os(Windows)
+#if os(Windows)
+#elseif os(WASI)
+    static func _setAttributes(_ attributes: [String : Data], at path: UnsafePointer<CChar>, followSymLinks: Bool) throws {
+        // WASI doesn't have extended attributes, so just ignore the request.
+    }
+#else
     static func _setAttribute(_ key: UnsafePointer<CChar>, value: Data, at path: UnsafePointer<CChar>, followSymLinks: Bool) throws {
         try value.withUnsafeBytes { buffer in
             #if canImport(Darwin)