Remove duplicates from binaries-shared-tests when creating make rules

This avoids a warning from make because binaries-shared-tests contains
both $(tests-container) and $(tests-internal).

Author: andreas-schwab

Rules

@@ -241,7 +241,7 @@ $(addprefix $(objpfx),$(binaries-shared-notests)): %: %.o \
 endif
 
 ifneq "$(strip $(binaries-shared-tests))" ""
-$(addprefix $(objpfx),$(binaries-shared-tests)): %: %.o \
+$(addprefix $(objpfx),$(sort $(binaries-shared-tests))): %: %.o \
   $(link-extra-libs-tests) \
   $(sort $(filter $(common-objpfx)lib%,$(link-libc))) \
   $(addprefix $(csu-objpfx),start.o) $(+preinit) $(+postinit)