fix incorrect display of downloaded files in the build script

This was due to stdout not being flushed in 659a072fe6eb646523d8feba8147dbd6842cc417

scripts/build.py

@@ -341,7 +341,8 @@ def download_file(url, dir, sha1):
     if hash != sha1:
         error('Checksum mismatch for %s' % name)
         os.remove(loc)
-    sys.stdout.write("\rDownloaded: %s [checksum OK]" % name)
+    sys.stdout.write("\rDownloaded: %s [checksum OK]\n" % name)
+    sys.stdout.flush()
     return loc
 
 def build_openssl(config, basedir):