fixup! Makefile: start moving to macro based Makefile target generation

scripts/helpers/rules.mk

@@ -4,32 +4,33 @@
 #
 # Generate build rules for files in variable <PREFIX>_SRCS. Use <PREFIX>_CFLAGS,
 # <PREFIX>_CXXFLAGS, <PREFIX>_ASFLAGS to control build flags.
+# Object files will be put into $BUILDDIR
 # E.g: 
 # $(eval $(call COMPILE_RULES,AM_))
 define COMPILE_RULES
-AM_OBJS := $(addprefix $(DST_DIR)/, $(addsuffix .o, $(AM_SRCS)))
+$(1)OBJS := $$(addprefix $$(BUILDDIR)/, $$(addsuffix .o, $$($(1)SRCS)))
 ### Rule (compile): a single `.c` -> `.c.o` (gcc)
-$$(filter %.c.o, $$($(1)OBJS)): $$(DST_DIR)/%.c.o: %.c
+$$(filter %.c.o, $$($(1)OBJS)): $$(BUILDDIR)/%.c.o: %.c
 	@mkdir -p $$(dir $$@) && echo + CC $$<
 	@$$(CC) $$($(1)CFLAGS) -c -o $$@ $$(realpath $$<)
 
 ### Rule (compile): a single `.cc` -> `.cc.o` (g++)
-$$(filter %.cc.o, $$($(1)OBJS)): $$(DST_DIR)/%.cc.o: %.cc
+$$(filter %.cc.o, $$($(1)OBJS)): $$(BUILDDIR)/%.cc.o: %.cc
 	@mkdir -p $$(dir $$@) && echo + CXX $$<
 	@$$(CXX) $$($(1)CXXFLAGS) -c -o $$@ $$(realpath $$<)
 
 ### Rule (compile): a single `.cpp` -> `.cpp.o` (g++)
-$$(filter %.cpp.o, $$($(1)OBJS)): $$(DST_DIR)/%.cpp.o: %.cpp
+$$(filter %.cpp.o, $$($(1)OBJS)): $$(BUILDDIR)/%.cpp.o: %.cpp
 	@mkdir -p $$(dir $$@) && echo + CXX $$<
 	@$$(CXX) $$($(1)CXXFLAGS) -c -o $$@ $$(realpath $$<)
 
 ### Rule (compile): a single `.S` -> `.S.o` (gcc, which preprocesses and calls as)
-$$(filter %.S.o, $$($(1)OBJS)): $$(DST_DIR)/%.S.o: %.S
+$$(filter %.S.o, $$($(1)OBJS)): $$(BUILDDIR)/%.S.o: %.S
 	@mkdir -p $$(dir $$@) && echo + AS $$<
 	@$$(AS) $$($(1)ASFLAGS) -c -o $$@ $$(realpath $$<)
 
 ### Rule (`#include` dependencies): paste in `.d` files generated by gcc on `-MMD`
--include $$(addprefix $$(DST_DIR)/, $$(addsuffix .d, $$(filter %.c %.cc, $$(AM_SRCS))))
+-include $$(addprefix $$(BUILDDIR)/, $$(addsuffix .d, $$(filter %.c %.cc, $$($(1)SRCS))))
 endef
 
 # Usage: