Workaround for CI failure due to Data.bytes not being present.

swift-ci still uses an older Xcode version with an older OS SDK that does not
include `Data.bytes`. As a result, Swift Testing fails to build for Apple
platforms. Work around the issue by manually constructing a `RawSpan` in the
relevant place.

Resolves rdar://169480914.

Author: grynspan

Sources/Testing/Support/JSON.swift

@@ -44,7 +44,10 @@ enum JSON {
     encoder.userInfo.merge(userInfo, uniquingKeysWith: { _, rhs in rhs})
 
     let data = try encoder.encode(value)
-    return try body(data.bytes)
+    // WORKAROUND for older SDK on swift-ci (rdar://169480914)
+    return try data.withUnsafeBytes { data in
+      try body(data.bytes)
+    }
 #else
     throw SystemError(description: "JSON encoding requires Foundation which is not available in this environment.")
 #endif