Fix Windows builds

Windows uses the argFile by default, which highlighted a bug: the
arg file was written in the output directory, which was cleaned
before running the task (cleaning is necessary or we'd have stale
files and up-to-date checking would be broken).

The arg file is now written in the temp directory instead.

Author: melix

native-gradle-plugin/src/functionalTest/groovy/org/graalvm/buildtools/gradle/JUnitFunctionalTests.groovy

@@ -45,7 +45,7 @@ import org.graalvm.buildtools.gradle.fixtures.AbstractFunctionalTest
 
 class JUnitFunctionalTests extends AbstractFunctionalTest {
     def "test if JUint support works with various annotations, reflection and resources"() {
-
+        debug=true
         given:
         withSample("junit-tests")
 

native-gradle-plugin/src/main/java/org/graalvm/buildtools/gradle/internal/NativeImageCommandLineProvider.java

@@ -234,8 +234,8 @@ public List<String> asArguments() {
 
         List<String> actualCliArgs;
         if (useArgFile.getOrElse(true)) {
-            Path argFileDir = Paths.get(workingDirectory.get());
-            actualCliArgs = new ArrayList<>(NativeImageUtils.convertToArgsFile(cliArgs, argFileDir, argFileDir));
+            Path argFileDir = Paths.get(System.getProperty("java.io.tmpdir"));
+            actualCliArgs = new ArrayList<>(NativeImageUtils.convertToArgsFile(cliArgs, argFileDir, Paths.get(workingDirectory.get())));
         } else {
             actualCliArgs = cliArgs;
         }