Remove --javac parameter

After switching ContikiMoteType to use
an Arena, this is no longer required.

build.gradle

@@ -118,10 +118,7 @@ tasks.register('fullJar', Jar) {
 run {
   // Bad Cooja location detected with gradle run, explicitly pass -cooja.
   doFirst {
-    args += ['--cooja', "$projectDir",
-             '--javac', javaToolchains.compilerFor {
-                         languageVersion = JavaLanguageVersion.of(javaVersion)
-                       }.get().executablePath]
+    args += ['--cooja', "$projectDir"]
   }
   // Connect stdin to make the MSPSim CLI work, except when running in CI.
   if (System.getenv('CI') == null) {

java/org/contikios/cooja/Cooja.java

@@ -1686,7 +1686,7 @@ public static void loadQuickHelp(final Object obj) {
    * values when creating a new simulation in the File menu.
    */
   public record Config(LogbackColors logColors, boolean vis, String externalToolsConfig,
-                       String logDir, String contikiPath, String coojaPath, String javac) {}
+                       String logDir, String contikiPath, String coojaPath) {}
 
   public record LogbackColors(String error, String warn, String info, String fallback) {}
   private record PathIdentifier(String id, String path) {}

java/org/contikios/cooja/Main.java

@@ -90,12 +90,6 @@ class Main {
   @Option(names = "--cooja", paramLabel = "DIR", description = "the Cooja directory")
   String coojaPath;
 
-  /**
-   * Option for specifying javac path.
-   */
-  @Option(names = "--javac", paramLabel = "FILE", description = "the javac binary")
-  String javac;
-
   /**
    * Option for specifying external user config file.
    */
@@ -295,22 +289,12 @@ public static void main(String[] args) {
       System.exit(1);
     }
 
-    if (options.mspSimPlatform == null && options.javac == null) {
-      System.err.println("Missing required option: '--javac=FILE'");
-      System.exit(1);
-    }
-
-    if (options.mspSimPlatform == null && !Files.exists(Path.of(options.javac))) {
-      System.err.println("Java compiler '" + options.javac + "' does not exist");
-      System.exit(1);
-    }
-
     if (options.mspSimPlatform == null) { // Start Cooja.
       // Use colors that are good on a dark background and readable on a white background.
       var colors = new LogbackColors(ANSIConstants.BOLD + "91", "96",
               ANSIConstants.GREEN_FG, ANSIConstants.DEFAULT_FG);
       var cfg = new Config(colors, options.gui, options.externalUserConfig,
-                options.logDir, options.contikiPath, options.coojaPath, options.javac);
+                options.logDir, options.contikiPath, options.coojaPath);
       Cooja.go(cfg, simConfigs);
     } else { // Start MSPSim.
       var config = new ArgumentManager(options.simulationFiles.toArray(new String[0]));