applied patch provied by Paul Boven fixing USB usage

Author: christopherpoole

Arduino.mk

@@ -337,9 +337,11 @@ ECHO    = echo
 SYS_LIBS      = $(patsubst %,$(ARDUINO_LIB_PATH)/%,$(ARDUINO_LIBS))
 SYS_INCLUDES  = $(patsubst %,-I%,$(SYS_LIBS))
 LIB_C_SRCS    = $(wildcard $(patsubst %,%/*.c,$(SYS_LIBS)))
+LIB_AS_SRCS   = $(wildcard $(patsubst %,%/*.S,$(SYS_LIBS)))
 LIB_CPP_SRCS  = $(wildcard $(patsubst %,%/*.cpp,$(SYS_LIBS)))
 LIB_OBJS      = $(patsubst $(ARDUINO_LIB_PATH)/%.c,$(OBJDIR)/libs/%.o,$(LIB_C_SRCS)) \
-		$(patsubst $(ARDUINO_LIB_PATH)/%.cpp,$(OBJDIR)/libs/%.o,$(LIB_CPP_SRCS))
+		$(patsubst $(ARDUINO_LIB_PATH)/%.cpp,$(OBJDIR)/libs/%.o,$(LIB_CPP_SRCS)) \
+		$(patsubst $(ARDUINO_LIB_PATH)/%.S,$(OBJDIR)/libs/%.o,$(LIB_AS_SRCS))
 
 CPPFLAGS      = -mmcu=$(MCU) -DF_CPU=$(F_CPU) -DARDUINO=$(ARDUINO_VERSION) \
 			-I. -I$(ARDUINO_CORE_PATH) -I$(ARDUINO_VAR_PATH)/$(VARIANT) \
@@ -370,6 +372,10 @@ $(OBJDIR)/libs/%.o: $(ARDUINO_LIB_PATH)/%.cpp
 	mkdir -p $(dir $@)
 	$(CC) -c $(CPPFLAGS) $(CXXFLAGS) $< -o $@
 
+$(OBJDIR)/libs/%.o: $(ARDUINO_LIB_PATH)/%.S
+	mkdir -p $(dir $@)
+	$(CC) -c $(CPPFLAGS) $(ASFLAGS) $< -o $@
+
 # normal local sources
 # .o rules are for objects, .d for dependency tracking
 # there seems to be an awful lot of duplication here!!!