Fixing issue in docs missing escape.

git-svn-id: https://svn.apache.org/repos/asf/maven/plugins/trunk@1739508 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/src/site/apt/index.apt.vm b/src/site/apt/index.apt.vm
index 6c601cf..9e160e9 100644
--- a/src/site/apt/index.apt.vm
+++ b/src/site/apt/index.apt.vm
@@ -61,7 +61,7 @@
         <version>${project.version}</version>
         <configuration>
           <archive>
-            <manifestFile>${project.build.outputDirectory}/META-INF/MANIFEST.MF</manifestFile>
+            <manifestFile>\${project.build.outputDirectory}/META-INF/MANIFEST.MF</manifestFile>
           </archive>
         </configuration>
         ...