Merge pull request #39 from lvscar/fix_file-write

make file manager set function truncate opened file at first

Author: colemancda

Sources/SwiftFoundation/FileManager.swift

@@ -212,7 +212,7 @@ public struct FileManager {
     public static func set(contents data: Data, at path: String) throws {
 
         // get file descriptor for path (open file)
-        let file = open(path, O_WRONLY)
+        let file = open(path, O_TRUNC | O_WRONLY)
 
         guard file != -1 else { throw POSIXError.fromErrno! }