Don't always run code in Ant task tests

But when running code, do it via <java> task, not via custom testing code. Most
of the time the compiled code need not be runned, because it's irrelevant to
the Ant task itself

compiler/testData/integration/ant/jvm/jvmClasspath/build.log.expected

@@ -4,6 +4,7 @@ Buildfile: [TestData]/build.xml
 build:
   [kotlinc] Compiling [[TestData]/hello.kt] => [[Temp]/hello.jar]
   [kotlinc] WARNING: [TestData]/hello.kt: (15, 9) Variable 'result' is never used
+     [java] OK
 
 BUILD SUCCESSFUL
 Total time: [time]