The package product 'SwiftSyntaxMacros' requires minimum platform version 10.15 for the macOS platform, but this target supports 10.13

Question

I created a new swift macro package in my Xcode project.

My Package.swift looks like:

import CompilerPluginSupport
import PackageDescription

let package = Package(
  name: "TestMockable",
  platforms: [.iOS(.v14)],
  products: [
    .library(
      name: "Test",
      targets: ["Test"]
    ),
  ],
  dependencies: [
    .package(url: "https://github.com/apple/swift-syntax.git", from: "509.0.0-swift-5.9-DEVELOPMENT-SNAPSHOT-2023-04-25-b"),
  ],
  targets: [
    .macro(
      name: "TestMacro",
      dependencies: [
        .product(name: "SwiftSyntaxMacros", package: "swift-syntax"),
        .product(name: "SwiftCompilerPlugin", package: "swift-syntax"),
      ]
    ),
    .target(
      name: "Test",
      dependencies: ["TestMacro"]
    ),
  ]
)

Without adding .macOS(.v10_15) in platforms:, I get the following errors

However, when I add platforms: [.iOS(.v14), .macOS(.v10_15)],, I get the following errors:

How can I solve it?