IDEA-118759: Run ant headless so no dock icon will appear

(https://github.com/JetBrains/intellij-community/pull/131 manually merged and improved)

build.xml

@@ -17,7 +17,7 @@
     <sequential>
       <java failonerror="true" jar="${project.home}/lib/ant/lib/ant-launcher.jar" fork="true">
         <jvmarg line="-Xmx612m -XX:MaxPermSize=152m"/>
-
+        <sysproperty key="java.awt.headless" value="true"/>
         <arg line="&quot;-Dgant.script=@{script}&quot;"/>
         <arg line="&quot;-Dteamcity.build.tempDir=${tmp.dir}&quot;"/>
         <arg line="&quot;-Didea.test.group=ALL_EXCLUDE_DEFINED&quot;"/>

build/scripts/utils.gant

@@ -757,6 +757,7 @@ binding.setVariable("buildWinLauncher", { String ch, String inputPath, String ou
   }
 
   ant.java(classname: "com.pme.launcher.LauncherGeneratorMain", fork: "true") {
+    sysproperty(key: "java.awt.headless", value: "true")
     arg(value: inputPath)
     arg(value: appInfo)
     arg(value: "$ch/native/WinLauncher/WinLauncher/resource.h")

python/build.xml

@@ -18,7 +18,7 @@
     <sequential>
       <java failonerror="true" jar="${project.home}/lib/ant/lib/ant-launcher.jar" fork="true">
         <jvmarg line="-Xmx612m -XX:MaxPermSize=152m -Didea.build.number=${idea.build.number} &quot;-DideaPath=${idea.path}&quot;"/>
-
+        <sysproperty key="java.awt.headless" value="true"/>
         <arg line="&quot;-Dgant.script=@{script}&quot;"/>
         <arg line="&quot;-Dteamcity.build.tempDir=${tmp.dir}&quot;"/>
         <arg line="&quot;-Didea.build.number=${idea.build.number}&quot;"/>