[NFC] Fix warnings (#603)

* [NFC] BridgeJS: Fix unused variable warning in BridgeJSCommandPlugin.swift

* [NFC] JavaScriptEventLoop: Fix warnings for undeclared SPI usage

Author: kateinoigakukun

Plugins/BridgeJS/Sources/BridgeJSCommandPlugin/BridgeJSCommandPlugin.swift

@@ -98,7 +98,6 @@ extension BridgeJSCommandPlugin.Context {
         printStderr("Generating bridge code for \(target.name)...")
 
         let generatedDirectory = target.directoryURL.appending(path: "Generated")
-        let generatedJavaScriptDirectory = generatedDirectory.appending(path: "JavaScript")
 
         let bridgeDtsPath = target.directoryURL.appending(path: "bridge-js.d.ts")
         let tsconfigPath = context.package.directoryURL.appending(path: "tsconfig.json")

Sources/JavaScriptEventLoop/JavaScriptEventLoop+ExecutorFactory.swift

@@ -4,7 +4,11 @@
 // See: https://github.com/swiftlang/swift/pull/80266
 // See: https://forums.swift.org/t/pitch-2-custom-main-and-global-executors/78437
 
+#if compiler(>=6.3)
 @_spi(ExperimentalCustomExecutors) import _Concurrency
+#else
+import _Concurrency
+#endif
 import _CJavaScriptKit
 
 #if compiler(>=6.3)

Sources/JavaScriptEventLoop/JavaScriptEventLoop.swift

@@ -1,5 +1,9 @@
 import JavaScriptKit
+#if compiler(>=6.3)
 @_spi(ExperimentalCustomExecutors) import _Concurrency
+#else
+import _Concurrency
+#endif
 import _CJavaScriptEventLoop
 import _CJavaScriptKit