Add SwiftIfConfig as a dependency for macro testing

Author: DougGregor

Package.swift

@@ -562,7 +562,7 @@ var targets: [Target] = [
       .product(name: "SwiftToolsSupport-auto", package: "swift-tools-support-core"),
       // Depend on `SwiftCompilerPlugin` and `SwiftSyntaxMacros` so the modules are built before running tests and can
       // be used by test cases that test macros (see `SwiftPMTestProject.macroPackageManifest`)
-    ] + swiftSyntaxDependencies(["SwiftParser", "SwiftSyntax", "SwiftCompilerPlugin", "SwiftSyntaxMacros"]),
+    ] + swiftSyntaxDependencies(["SwiftIfConfig", "SwiftParser", "SwiftSyntax", "SwiftCompilerPlugin", "SwiftSyntaxMacros"]),
     swiftSettings: globalSwiftSettings
   ),
 

Sources/SKTestSupport/SwiftPMTestProject.swift

@@ -105,6 +105,7 @@ package class SwiftPMTestProject: MultiFileTestProject {
         "SwiftCompilerPlugin",
         "SwiftCompilerPluginMessageHandling",
         "SwiftDiagnostics",
+        "SwiftIfConfig",
         "SwiftOperators",
         "SwiftParser",
         "SwiftParserDiagnostics",