Build JSI, React-Debug and React-logger with SPM (#50075)

Summary:

This is an exploratory change to see how it will look like to build core from SPM.

In this change we are building three pieces of React native (using the Podspec names for simplicity):
- React-jsi
- React-debug
- React-logger

They depends on a local ReactNativeDependency.xcframework we can build using the prebuild-io script.

## CHANGELOG:
[INTERNAL] - set up initial Swift PM configuration

Differential Revision: D70567840

Author: cipolleschi

packages/react-native/Package.swift

@@ -0,0 +1,112 @@
+// swift-tools-version: 6.0
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+import PackageDescription
+
+let react = "React"
+
+let cxxRNDepHeaderSearchPath: (Int) -> CXXSetting = {
+  let prefix = (0..<$0).map { _ in "../" } .joined(separator: "")
+  return .headerSearchPath("\(prefix)third-party/ReactNativeDependencies.xcframework/Headers")
+}
+let cRNDepHeaderSearchPath: (Int) -> CSetting = {
+  let prefix = (0..<$0).map { _ in "../" } .joined(separator: "")
+  return .headerSearchPath("\(prefix)third-party/ReactNativeDependencies.xcframework/Headers")
+}
+
+
+let package = Package(
+    name: react,
+    products: [
+        .library(
+            name: react,
+            type: .dynamic,
+            targets: [.reactDebug, .jsi, .logger, .mapbuffer]
+        ),
+    ],
+    targets: [
+       .reactNativeTarget(
+         name: .reactDebug,
+         dependencies: [.reactNativeDependencies],
+         path: "ReactCommon/react/debug",
+         publicHeadersPath: "."
+       ),
+       .reactNativeTarget(
+          name: .jsi,
+          dependencies: [.reactNativeDependencies],
+          path: "ReactCommon/jsi",
+          extraExcludes: ["jsi/CMakeLists.txt", "jsi/test/testlib.h", "jsi/test/testlib.cpp"],
+          sources: ["jsi"],
+          publicHeadersPath: "jsi/",
+          extraCSettings: [.headerSearchPath(".")],
+          extraCxxSettings: [.headerSearchPath(".")]
+       ),
+      .reactNativeTarget(
+        name: .logger,
+        dependencies: [.reactNativeDependencies, .jsi],
+        path: "ReactCommon/logger",
+        publicHeadersPath: "."
+      ),
+      .reactNativeTarget(
+        name: .mapbuffer,
+        dependencies: [.reactNativeDependencies, .reactDebug],
+        path: "ReactCommon/react/renderer/mapbuffer",
+        extraExcludes: ["tests/MapBufferTest.cpp"],
+        publicHeadersPath: ".",
+        extraCSettings: [.headerSearchPath("../../..")],
+        extraCxxSettings: [.headerSearchPath("../../..")]
+       ),
+      .binaryTarget(
+        name: .reactNativeDependencies,
+        path: "third-party/ReactNativeDependencies.xcframework"
+      ),
+    ]
+)
+
+extension String {
+  static let reactDebug = "React-debug"
+  static let jsi = "React-jsi"
+  static let logger = "React-logger"
+  static let mapbuffer = "React-Mapbuffer"
+
+  static let reactNativeDependencies = "ReactNativeDependencies"
+}
+
+func defaultExcludeFor(module: String) -> [String] {
+  return ["BUCK", "CMakeLists.txt", "\(module).podspec"]
+}
+
+extension Target {
+  static func reactNativeTarget(
+    name: String,
+    dependencies: [String],
+    path: String,
+    extraExcludes: [String] = [],
+    sources: [String]? = nil,
+    publicHeadersPath: String? = nil,
+    extraCSettings: [CSetting] = [],
+    extraCxxSettings: [CXXSetting] = []
+  ) -> Target {
+    let dependencies = dependencies.map { Dependency.byNameItem(name: $0, condition: nil) }
+    let excludes = defaultExcludeFor(module: .logger) + extraExcludes
+    let numOfSlash = path.count { $0 == "/"}
+    let cSettings = [cRNDepHeaderSearchPath(numOfSlash + 1)] + extraCSettings
+    let cxxSettings = [cxxRNDepHeaderSearchPath(numOfSlash + 1), .unsafeFlags(["-std=c++20"])] + extraCxxSettings
+    
+    return .target(
+      name: name,
+      dependencies: dependencies,
+      path: path,
+      exclude: excludes,
+      sources: sources,
+      publicHeadersPath: publicHeadersPath,
+      cSettings: cSettings,
+      cxxSettings: cxxSettings
+    )
+  }
+}