re-enable multiple threads

Author: d-kozak

substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/NativeImageOptions.java

@@ -147,7 +147,7 @@ public static CStandards getCStandard() {
      * Configures the number of threads used by the {@link CompletionExecutor}.
      */
     @Option(help = "The maximum number of threads to use concurrently during native image generation.")//
-    public static final HostedOptionKey<Integer> NumberOfThreads = new HostedOptionKey<>(Math.min(Runtime.getRuntime().availableProcessors(), 1));
+    public static final HostedOptionKey<Integer> NumberOfThreads = new HostedOptionKey<>(Math.min(Runtime.getRuntime().availableProcessors(), 32));
 
     /*
      * Analysis scales well up to 12 cores and gives slight improvements until 18 cores. We set the