Speed up compilation by not using recusive make

The cleaning is done outside the targets, by checking the
requested target name.

tmk_core/rules.mk

@@ -271,23 +271,10 @@ ALL_CPPFLAGS = $(MCUFLAGS) -x c++ $(CPPFLAGS) $(GENDEPFLAGS) $(EXTRAFLAGS)
 ALL_ASFLAGS = $(MCUFLAGS) -x assembler-with-cpp $(ASFLAGS) $(EXTRAFLAGS)
 
 # Default target.
-all:
-	@$(MAKE) begin
-	@$(MAKE) gccversion
-	@$(MAKE) sizebefore
-	@$(MAKE) clean_list # force clean each time
-	@$(MAKE) build
-	@$(MAKE) sizeafter
-	@$(MAKE) end
+all: build sizeafter
 
 # Quick make that doesn't clean
-quick:
-	@$(MAKE) begin
-	@$(MAKE) gccversion
-	@$(MAKE) sizebefore
-	@$(MAKE) build
-	@$(MAKE) sizeafter
-	@$(MAKE) end
+quick: build sizeafter
 
 # Change the build target to build a HEX file or a library.
 build: elf hex
@@ -303,13 +290,7 @@ sym: $(BUILD_DIR)/$(TARGET).sym
 LIBNAME=lib$(TARGET).a
 lib: $(LIBNAME)
 
-
-
-# Eye candy.
-# AVR Studio 3.x does not check make's exit code but relies on
-# the following magic strings to be generated by the compile job.
-begin:
-	@$(SECHO) $(MSG_BEGIN)
+check_submodule:
 	git submodule status --recursive | \
 	while IFS= read -r x; do \
 		case "$$x" in \
@@ -318,10 +299,6 @@ begin:
 		esac \
 	done
 
-end:
-	@$(SECHO) $(MSG_END)
-
-
 # Display size of file.
 HEXSIZE = $(SIZE) --target=$(FORMAT) $(TARGET).hex
 #ELFSIZE = $(SIZE) --mcu=$(MCU) --format=avr $(TARGET).elf
@@ -331,7 +308,7 @@ sizebefore:
 	@if test -f $(TARGET).hex; then $(SECHO) $(MSG_SIZE_BEFORE); $(SILENT) || $(HEXSIZE); \
 	2>/dev/null; $(SECHO); fi
 
-sizeafter:
+sizeafter: $(BUILD_DIR)/$(TARGET).hex
 	@if test -f $(TARGET).hex; then $(SECHO); $(SECHO) $(MSG_SIZE_AFTER); $(SILENT) || $(HEXSIZE); \
 	2>/dev/null; $(SECHO); fi
 	# test file sizes eventually
@@ -386,9 +363,9 @@ gccversion :
 # Link: create ELF output file from object files.
 .SECONDARY : $(BUILD_DIR)/$(TARGET).elf
 .PRECIOUS : $(OBJ)
-%.elf: $(OBJ)
+%.elf: gccversion sizebefore check_submodule $(OBJ)
 	@$(SILENT) || printf "$(MSG_LINKING) $@" | $(AWK_CMD)
-	$(eval CMD=$(CC) $(ALL_CFLAGS) $^ --output $@ $(LDFLAGS))
+	$(eval CMD=$(CC) $(ALL_CFLAGS) $(OBJ) --output $@ $(LDFLAGS))
 	@$(BUILD_CMD)
 
 # Compile: create object files from C source files.
@@ -429,14 +406,7 @@ $(OBJDIR)/%.o : %.S
 	$(CC) -E -mmcu=$(MCU) $(CFLAGS) $< -o $@
 
 # Target: clean project.
-clean: begin clean_list end
-
-clean_list :
-	@$(REMOVE) -r $(BUILD_DIR)
-	@$(REMOVE) -r $(TOP_DIR)/$(BUILD_DIR)
-	@$(REMOVE) -r $(KEYBOARD_PATH)/$(BUILD_DIR)
-	@if $$SUBPROJECT; then $(REMOVE) -r $(SUBPROJECT_PATH)/$(BUILD_DIR); fi
-	@$(REMOVE) -r $(KEYMAP_PATH)/$(BUILD_DIR)
+clean: 
 
 show_path:
 	@echo VPATH=$(VPATH)
@@ -496,6 +466,19 @@ all-keymaps-%:
 
 all-keymaps: all-keymaps-all
 
+GOAL=$(MAKECMDGOALS)
+ifeq ($(MAKECMDGOALS),)
+GOAL = all
+endif
+CLEANING_GOALS=clean clean_list all
+ifneq ($(findstring $(GOAL),$(CLEANING_GOALS)),)
+$(shell $(REMOVE) -r $(BUILD_DIR) 2>/dev/null)
+$(shell $(REMOVE) -r $(TOP_DIR)/$(BUILD_DIR))
+$(shell $(REMOVE) -r $(KEYBOARD_PATH)/$(BUILD_DIR))
+$(shell if $$SUBPROJECT; then $(REMOVE) -r $(SUBPROJECT_PATH)/$(BUILD_DIR); fi)
+$(shell $(REMOVE) -r $(KEYMAP_PATH)/$(BUILD_DIR))
+endif
+
 # Create build directory
 $(shell mkdir $(BUILD_DIR) 2>/dev/null)
 
@@ -508,7 +491,7 @@ $(shell mkdir $(OBJDIR) 2>/dev/null)
 
 
 # Listing of phony targets.
-.PHONY : all quick begin finish end sizebefore sizeafter gccversion \
+.PHONY : all quick finish sizebefore sizeafter gccversion \
 build elf hex eep lss sym coff extcoff \
 clean clean_list debug gdb-config show_path \
 program teensy dfu flip dfu-ee flip-ee dfu-start \