[build] the build can now autoclean

autocleaning means that the build system detects that the usual incremental mode,
where the build artefacts are not deleted and instead used to skip steps already performed,
is not an option due to changes in the build script itself or a change in deps not detectable.

It works by having a version number which can be incremented, and a system that checks
for mismatches and forces a clean.

buildScripts/compile.ant.xml

@@ -27,7 +27,7 @@ This buildfile is part of projectlombok.org. It takes care of compiling and buil
 	<property name="mapstruct-binding.version" value="0.2.0" />
 	
 	<!-- compiles just 'version.java' and runs the produced class file, setting up the various version properties -->
-	<target name="version" depends="ipp.setup, deps.jdk-runtime" description="Shows the version number" unless="lombok.version">
+	<target name="version" depends="ipp.setup, deps.jdk-runtime, -setup.build" description="Shows the version number" unless="lombok.version">
 		<mkdir dir="build/lombok" />
 		<ivy:compile destdir="build/lombok" source="1.5" target="1.5" ecj="true" nowarn="true">
 			<bootclasspath path="${jdk6-rt.loc}" />
@@ -51,7 +51,7 @@ This buildfile is part of projectlombok.org. It takes care of compiling and buil
 		<echo level="info">Lombok version: ${lombok.version} (${lombok.fullversion})</echo>
 	</target>
 	
-	<target name="compile" depends="version, deps" description="Compiles the code">
+	<target name="compile" depends="version, deps, -setup.build" description="Compiles the code">
 		<!--
 			1. Compile stubs.
 			2. Compile lombok-utils.
@@ -218,7 +218,7 @@ lombok.launch.AnnotationProcessorHider$ClaimingProcessor,isolating</echo>
 	</target>
 	
 	<!-- compiles the bit of API from mapstruct that lombok compiles against. -->
-	<target name="mapstruct.compile">
+	<target name="mapstruct.compile" depends="-setup.build">
 		<mkdir dir="build/mapstruct" />
 		<ivy:compile destdir="build/mapstruct" release="8">
 			<src path="src/j9stubs" />
@@ -294,7 +294,7 @@ lombok.launch.AnnotationProcessorHider$ClaimingProcessor,isolating</echo>
 		<property name="lombok.dist.built" value="true" />
 	</target>
 	
-	<target name="compile.support" depends="ipp.setup, deps" description="Compiles code that is used solely by the build, such as website and IDE project creation">
+	<target name="compile.support" depends="ipp.setup, deps, -setup.build" description="Compiles code that is used solely by the build, such as website and IDE project creation">
 		<ivy:compile includeDestClasses="false" includeantruntime="false" destdir="build/support" debug="on" source="1.8" target="1.8">
 			<compilerarg value="-proc:none" />
 			<compilerarg value="-Xlint:-options" />