Merge pull request #12796 from linux-on-ibm-z/master_s390x_KeyPath

fixed test case KeyPath.swift for s390x

Author: jckarter

stdlib/public/core/KeyPath.swift

@@ -2390,8 +2390,8 @@ internal func _instantiateKeyPathBuffer(
         // offset within the metadata object.
         let metadataPtr = unsafeBitCast(base, to: UnsafeRawPointer.self)
         let offsetOfOffset = patternBuffer.pop(UInt32.self)
-        let offset = metadataPtr.load(fromByteOffset: Int(offsetOfOffset),
-                                      as: UInt32.self)
+        let offset = UInt32(metadataPtr.load(fromByteOffset: Int(offsetOfOffset),
+                                       as: UInt.self))
         // Rewrite the header for a resolved offset.
         var newHeader = header
         newHeader.payload = RawKeyPathComponent.Header.outOfLineOffsetPayload