Don't copy DISTFILES during bootstrapping

DISTFILES are necessary only during bootstrapping and should not be
distributed.

This partially reverts commit 9f0e54ab2.

bootstrap.conf

@@ -77,7 +77,7 @@ getopt-gnu
 
 # copy_files srcdir dstdir
 copy_files() {
-  for file in DISTFILES `cat $1/DISTFILES`
+  for file in `cat $1/DISTFILES`
   do
     case $file in
     "#*")  continue;;