Make build of GUI components optional (default)

These presently don't work if you are using reasonably current versions
of JDK and SWT.  Made this optional if you just run ant, but left it
enabled by default since it ought to be fixed.  Linux build scripts may
just provide an ACBuild.properties that turns it off so that e.g., the
ant build helper doesn't need any custom configuration.

build/ACBuild-default.properties

@@ -16,3 +16,4 @@ junitPathMac=/Users/Shared/eclipse/plugins/org.junit_3.8.2.v200706111738/junit.j
 junitPathUnix=/usr/share/java/junit.jar
 keyconf=${user.home}/.secret
 alias=name
+buildGui=true

build/build.xml

@@ -71,6 +71,9 @@
 		<property name="antjar" value="${antJarPathMac}" />
 		<property name="swtjar" value="${swtJarPathMac}" />
 		<property name="juintjar" value="${junitPathMac}" />
+		<condition property="buildMacGui" value="true">
+			<istrue value="buildGui" />
+		</condition>
 	</target>
 
 	<target name="init-unix" if="isUnix">
@@ -118,7 +121,8 @@
 		</signjar>
 	</target>
 
-	<target name="executableGuiJar" depends="init" description="Build GUI executable JAR">
+	<target name="executableGuiJar" depends="init" if="buildGui"
+		description="Build GUI executable JAR">
 		<javac srcdir="${source}" destdir="${classes}" classpath="${antjar}:${swtjar}">
 			<include name="**/*.java"/>
 			<exclude name="**/*Test.java"/>
@@ -161,7 +165,8 @@
 		</jar>
 	</target>
 
-	<target name="macBundle" depends="init,jars" description="Build Mac application bundle.">
+	<target name="macBundle" depends="init,jars" if="buildMacGui"
+		description="Build Mac application bundle.">
 		<property name="mac.dir" value="mac"/>
 		<property name="mac.app" value="${mac.dir}/AppleCommander.app"/>
 		<property name="mac.Contents" value="${mac.app}/Contents"/>