Patch from Matt Kraai to fix debian bug #227081

cp does not truncate existing destinations.  That is, after
running

 echo foo > foo
 echo fubar > fubar
 cp foo fubar

the contents of fubar are

 foo
 r

instead of

 foo

1 files changed, 1 insertions, 1 deletions

diff --git a/libbb/copy_file.c b/libbb/copy_file.c
index ffdb8242b..7ddb9a23f 100644
--- a/libbb/copy_file.c
+++ b/libbb/copy_file.c
@@ -153,7 +153,7 @@ int copy_file(const char *source, const char *dest, int flags)
                                 }
                         }
 
-                        dst_fd = open(dest, O_WRONLY);
+                        dst_fd = open(dest, O_WRONLY|O_TRUNC);
                         if (dst_fd == -1) {
                                 if (!(flags & FILEUTILS_FORCE)) {
                                         bb_perror_msg("unable to open `%s'", dest);