Fix "ar" flags in some Makefiles to allow for silent "make -s"
diff --git a/cpu/at32ap/Makefile b/cpu/at32ap/Makefile
index 8ce79e9..f62ec8b 100644
--- a/cpu/at32ap/Makefile
+++ b/cpu/at32ap/Makefile
@@ -38,7 +38,7 @@
 all: $(obj).depend $(START) $(LIB)
 
 $(LIB): $(OBJS)
-	$(AR) crv $@ $^
+	$(AR) $(ARFLAGS) $@ $^
 
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