Use a CachingOutputStream when using the build context (#64)

The CachingOutputStream provides a write cache so that the target file is only modified if there's a content change.  If the data written exactly maps the existing content of the file, the file will not be modified at all.

Author: gnodet

src/main/java/org/codehaus/plexus/build/DefaultBuildContext.java

@@ -26,6 +26,7 @@
 
 import org.codehaus.plexus.util.DirectoryScanner;
 import org.codehaus.plexus.util.Scanner;
+import org.codehaus.plexus.util.io.CachingOutputStream;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -76,7 +77,7 @@ public boolean hasDelta(List<String> relpaths) {
 
   /** {@inheritDoc} */
   public OutputStream newFileOutputStream(File file) throws IOException {
-    return Files.newOutputStream(file.toPath());
+    return new CachingOutputStream(file.toPath());
   }
 
   /** {@inheritDoc} */