t/Makefile cleanup

t/Makefile now does not use double-colon rules (why would it?), the rm
-fr trash in the all rule is silent, and OPTS aren't set to blank so
that they can be taken from the environment.

t/Makefile

@@ -3,13 +3,12 @@
 # Copyright (c) 2005 Junio C Hamano
 #
 #OPTS=--verbose --debug
-OPTS=
 
 T = $(wildcard t[0-9][0-9][0-9][0-9]-*.sh)
 
-all::
+all:
 	@$(foreach t,$T,echo "*** $t ***"; sh $t $(OPTS) || exit; )
-	rm -fr trash
+	@rm -fr trash
 
-clean::
+clean:
 	rm -fr trash