Enable libcurl websocket support for Android SDK

[marcprux]

As reported at skiptools/skip#559 and https://github.com/orgs/skiptools/discussions/568, the Swift SDK for Android's libcurl used by FoundationNetworking is not being built with websockets support, resulting in a fatalError when trying to use URLSession.websocketTask() or URLSessionWebSocketTask:

marc@zap wsdemo % skip android run WSDemo
[0/1] Planning build
Building for debugging...
[0/4] Write swift-version-26D6868F3D3D2BFA.txt
[2/6] Compiling WSDemo WSDemo.swift
[3/6] Emitting module WSDemo
[4/7] Wrapping AST for WSDemo for debugging
[5/7] Write Objects.LinkFileList
[6/7] Linking WSDemo
Build complete! (0.54s)
[✓] Check Swift Package (0.2s)
[✓] Connecting to Android (0.08s)
[✓] Copying executable files (0.29s)
Swift/ErrorType.swift:254: Fatal error: Error raised at top level: Error Domain=NSURLErrorDomain Code=-1002 "(null)"UserInfo={NSErrorFailingURLKey=wss://echo.websocket.org, NSLocalizedDescription=WebSockets not supported by libcurl, NSErrorFailingURLStringKey=wss://echo.websocket.org}
Current stack trace:
0    libswiftCore.so                    0x000000769f68d3c8 swift_reportError + 44
1    libswiftCore.so                    0x000000769f727248 _swift_stdlib_reportFatalErrorInFile + 128
2    libswiftCore.so                    0x000000769f3dc92c <unavailable> + 1841452
3    libswiftCore.so                    0x000000769f538d14 _assertionFailure(_:_:file:line:flags:) + 160
4    libswiftCore.so                    0x000000769f586110 swift_errorInMain + 628
5    WSDemo                             0x0000005ac350f2b8 <unavailable> + 12984
6    libswift_Concurrency.so            0x00000076a20d6640 <unavailable> + 558656
7    libswift_Concurrency.so            0x00000076a20d7284 swift_job_run + 164
8    libdispatch.so                     0x00000076a1f10bf0 <unavailable> + 240624
9    libdispatch.so                     0x00000076a1f11604 <unavailable> + 243204
10   libdispatch.so                     0x00000076a1f176e8 <unavailable> + 268008
11   libc.so                            0x00000076a51256ac <unavailable> + 833196
12   libc.so                            0x00000076a50c2220 <unavailable> + 426528
Trap 

All we need to do is turn it on with ENABLE_WEBSOCKETS=ON. When building this PR separately (see artifacts at https://github.com/swift-android-sdk/swift-docker/actions/runs/20467831234) and copying over the new libFoundationNetworking.so, the test passes:

marc@zap wsdemo % skip android run WSDemo
Building for debugging...
[0/3] Write swift-version-26D6868F3D3D2BFA.txt
Build complete! (0.10s)
[✓] Check Swift Package (0.21s)
[✓] Connecting to Android (0.02s)
[✓] Copying executable files (0.28s)
received string: Request served by 4d896d95b55478
received string: Hello from Swift!

CC @swiftlang/android-workgroup
@al45tair: you may want to do the same for the Static SDK, since I expect you would also see similar websocket failures.

Here's the full test program for reference:

import Foundation
#if canImport(FoundationNetworking)
import FoundationNetworking
#endif
#if canImport(AndroidNative)
import AndroidNative
#endif

@main
struct WSDemo {
    static func main() async throws {
        #if os(Android)
        try AndroidBootstrap.setupCACerts() // needed in order to use https
        #endif

        let session = URLSession(configuration: .default)
        let url = URL(string: "wss://echo.websocket.org")!
        let webSocketTask = session.webSocketTask(with: url)
        webSocketTask.resume()
        defer { webSocketTask.cancel(with: .normalClosure, reason: nil) }

        _ = try await receiveString() // initial connect message like "Request served by 4d896d95b55478"

        let messageToSend = "Hello from Swift!"
        let message = URLSessionWebSocketTask.Message.string(messageToSend)
        try await webSocketTask.send(message)
        let response = try await receiveString()
        assert(messageToSend == response)

        func receiveString() async throws -> String {
            let receivedMessage = try await webSocketTask.receive()
            switch receivedMessage {
            case .string(let string):
                print("received string: \(string)")
                return string
            case .data(let data):
                fatalError("received data: \(data)")
            @unknown default:
                fatalError("Received unknown message type")
            }
        }
    }
}

[finagolfin]

I see that this has already been enabled last year in the Windows Powershell script, swiftlang/swift#73378.