copy the new unicode file to /lib/unicode on differences, not on
no differences.  this also fixes a builds when /lib/unicode needs
updating

Reference: /n/atom/patch/applied2013/runetypemk
Date: Thu Aug  1 21:57:06 CES 2013
Signed-off-by: quanstro@quanstro.net

--- /sys/src/cmd/runetype/mkfile	Thu Aug  1 21:56:01 2013
+++ /sys/src/cmd/runetype/mkfile	Thu Aug  1 21:56:02 2013
@@ -83,7 +83,7 @@
 	rm -f *.[$OS] [$OS].* y.tab.? lex.yy.c y.debug y.output $CLEANFILES
 
 /lib/unicode: unicode
-	diff -c unicode /lib/unicode && cp unicode /lib/unicode
+	diff -c unicode /lib/unicode || cp unicode /lib/unicode
 
 unicode:D: unicode.rc unicodedata
 	unicode.rc unicodedata