Confusing unsafeFlags in SwiftPM

Using Swift
1

I try build package WebSocketClient in Xcode failed with an error 'openssl/ssl.h' file not found.

However, it works when build in terminal using command swift build -Xcc -I/usr/local/libressl-3.5.1/include -Xcc -I/usr/local/websockets-4.3.1/include.

How do I resolve this problem using unsafeFlags in Xcode?

// swift-tools-version: 5.6
// The swift-tools-version declares the minimum version of Swift required to build this package.

import PackageDescription

let package = Package(
    name: "WebSocketClient",
    products: [
        // Products define the executables and libraries a package produces, and make them visible to other packages.
        .library(
            name: "WebSocketClient",
            targets: ["WebSocketClient"]),
    ],
    dependencies: [
        // Dependencies declare other packages that this package depends on.
        // .package(url: /* package url */, from: "1.0.0"),
    ],
    targets: [
        // Targets are the basic building blocks of a package. A target can define a module or a test suite.
        // Targets can depend on other targets in this package, and on products in packages this package depends on.
        .target(
            name: "WebSocketClient",
            dependencies: ["CLibWebSockets"]),
        .target(
            name: "CLibWebSockets",
            dependencies: [],
            cSettings: [
                .unsafeFlags(["-I/usr/local/libressl-3.5.1/include",
                              "-I/usr/local/websockets-4.3.1/include"])
            ]),
        .testTarget(
            name: "WebSocketClientTests",
            dependencies: ["WebSocketClient"]),
    ]
)