Add missing dependency

Author: neonichu

Package.swift

@@ -62,7 +62,8 @@ let package = Package(
       name: "SwiftDriverExecution",
       dependencies: [
         "SwiftDriver",
-        .product(name: "SwiftToolsSupport-auto", package: "swift-tools-support-core")
+        .product(name: "SwiftToolsSupport-auto", package: "swift-tools-support-core"),
+        .product(name: "llbuild", package: "swift-llbuild"),
       ],
       exclude: ["CMakeLists.txt"]),