Revert "common.mk: allow brace expansion for benchmark targets"

This reverts commit 4c0e21add7
because we're not using /bin/bash.

See 11d3986d65 and
1b2b0e1f24 to know its context.
In short, 4c0e21add7 does not work on
Ubuntu.

common.mk

@@ -1165,7 +1165,7 @@ bisect-ruby: PHONY
 COMPARE_RUBY = $(BASERUBY)
 BENCH_RUBY = $(RUNRUBY)
 ITEM =
-ARGS = $$(ls $(srcdir)/benchmark/*$(ITEM)*.{yml,rb} 2>/dev/null)
+ARGS = $$(find $(srcdir)/benchmark -maxdepth 1 -name '*$(ITEM)*.yml' -o -name '*$(ITEM)*.rb' | sort)
 OPTS =
 
 # You can pass several options through OPTS environment variable.