Use local git package

Author: kimdv

CodeGeneration/Package.swift

@@ -1,6 +1,7 @@
 // swift-tools-version:5.7
 
 import PackageDescription
+import Foundation
 
 let package = Package(
   name: "CodeGeneration",
@@ -11,8 +12,7 @@ let package = Package(
     .executable(name: "generate-swiftsyntax", targets: ["generate-swiftsyntax"])
   ],
   dependencies: [
-    .package(url: "https://github.com/apple/swift-syntax.git", revision: "94120e0cf9bf541e54fbc8512934daea23a9ad0c"),
-    .package(url: "https://github.com/apple/swift-argument-parser.git", .upToNextMinor(from: "1.2.2")),
+    .package(path: ".."),
   ],
   targets: [
     .executableTarget(
@@ -41,3 +41,14 @@ let package = Package(
     ),
   ]
 )
+
+if ProcessInfo.processInfo.environment["SWIFTCI_USE_LOCAL_DEPS"] == nil {
+    // Building standalone.
+    package.dependencies += [
+        .package(url: "https://github.com/apple/swift-argument-parser.git", .upToNextMinor(from: "1.2.2")),
+    ]
+} else {
+    package.dependencies += [
+        .package(path: "../../swift-argument-parser"),
+    ]
+}