Avoid warnings on Swift 5.1

Sources/xcodeproj/Extensions/String+md5.swift

@@ -25,8 +25,10 @@ import Foundation
 extension String {
     var md5: String {
         if let data = data(using: .utf8, allowLossyConversion: true) {
-            let message = data.withUnsafeBytes { bytes -> [UInt8] in
-                Array(UnsafeBufferPointer(start: bytes, count: data.count))
+            let message = data.withUnsafeBytes { bufferPointer in
+                Array(UnsafeBufferPointer(
+                    start: bufferPointer.baseAddress?.assumingMemoryBound(to: UInt8.self),
+                    count: data.count))
             }
 
             let MD5Calculator = MD5(message)
@@ -215,7 +217,7 @@ class MD5: HashProtocol {
 
         for chunk in BytesSequence(chunkSize: chunkSizeBytes, data: tmpMessage) {
             // break chunk into sixteen 32-bit words M[j], 0 ≤ j ≤ 15
-            var M = toUInt32Array(chunk)
+            let M = toUInt32Array(chunk)
             assert(M.count == 16, "Invalid array")
 
             // Initialize hash value for this chunk:

Sources/xcodeproj/Utils/PBXBatchUpdater.swift

@@ -119,7 +119,7 @@ public final class PBXBatchUpdater {
         if let fileParentGroup = try lazilyInstantiateGroups()[groupPath] {
             return (fileParentGroup, groupPath)
         }
-        var components = groupPath.components
+        let components = groupPath.components
         let componentsCount = components.count - 1
         for componentIndex in (0 ... componentsCount).reversed() {
             let currentPathComponents = components[0 ... componentIndex]

Sources/xcodeproj/Utils/ReferenceGenerator.swift

@@ -324,7 +324,7 @@ extension ReferenceGenerator {
             }
         case .xcode:
             let reference = "\(acronym)_\(typeNameAndIdentifiers)_\(counter)".md5.uppercased()
-            return String(reference.substring(to: reference.index(reference.startIndex, offsetBy: 24)))
+            return String(reference[...reference.index(reference.startIndex, offsetBy: 24)])
         }
     }
 }