py: Add LIBS_USERMOD to LIBS.

This enables C++ modules to correctly postion -l
linker flags at the end of the flags instead of at
the start. Updated the example C++ micropython.mk
accordingly.

Signed-off-by: Dryw Wade <dryw.wade@sparkfun.com>

Author: sfe-SparkFro

examples/usercmodule/cppexample/micropython.mk

@@ -8,5 +8,8 @@ SRC_USERMOD_CXX += $(CPPEXAMPLE_MOD_DIR)/example.cpp
 CFLAGS_USERMOD += -I$(CPPEXAMPLE_MOD_DIR)
 CXXFLAGS_USERMOD += -I$(CPPEXAMPLE_MOD_DIR) -std=c++11
 
+# Add any necessary paths to library files.
+# LDFLAGS_USERMOD += -Lpath/to/libs
+
 # We use C++ features so have to link against the standard library.
-LDFLAGS_USERMOD += -lstdc++
+LIBS_USERMOD += -lstdc++

py/py.mk

@@ -47,6 +47,7 @@ SRC_USERMOD_LIB_ASM :=
 CFLAGS_USERMOD :=
 CXXFLAGS_USERMOD :=
 LDFLAGS_USERMOD :=
+LIBS_USERMOD :=
 
 # Backwards compatibility with older user c modules that set SRC_USERMOD
 # added to SRC_USERMOD_C below
@@ -69,6 +70,7 @@ SRC_USERMOD_PATHFIX_LIB_ASM += $(patsubst $(USER_C_MODULES)/%.S,%.S,$(SRC_USERMO
 CFLAGS += $(CFLAGS_USERMOD)
 CXXFLAGS += $(CXXFLAGS_USERMOD)
 LDFLAGS += $(LDFLAGS_USERMOD)
+LIBS += $(LIBS_USERMOD)
 
 SRC_QSTR += $(SRC_USERMOD_PATHFIX_C) $(SRC_USERMOD_PATHFIX_CXX)
 PY_O += $(addprefix $(BUILD)/, $(SRC_USERMOD_PATHFIX_C:.c=.o))