make MockHashAlgorithm thread safe

Author: tomerd

Sources/SPMTestSupport/MockHashAlgorithm.swift

@@ -6,24 +6,25 @@
 
  See http://swift.org/LICENSE.txt for license information
  See http://swift.org/CONTRIBUTORS.txt for Swift project authors
-*/
+ */
 
+import Basics
 import TSCBasic
 
 public class MockHashAlgorithm: HashAlgorithm {
     public typealias Hash = (ByteString) -> ByteString
 
-    public private(set) var hashes: [ByteString] = []
+    public private(set) var hashes = ThreadSafeArrayStore<ByteString>()
     private var hashFunction: Hash!
 
     public init(hash: Hash? = nil) {
-        hashFunction = hash ?? { hash in
+        self.hashFunction = hash ?? { hash in
             self.hashes.append(hash)
             return ByteString(hash.contents.reversed())
         }
     }
 
     public func hash(_ bytes: ByteString) -> ByteString {
-        return hashFunction(bytes)
+        return self.hashFunction(bytes)
     }
 }