Refactor quantum/split_common/i2c.c, quantum/split_common/serial.c (#4522)

* add temporary compile test shell script

* Extended support of SKIP_VERSION to make invariant compile results during testing.

* build_keyboard.mk, tmk_core/rules.mk: add LIB_SRC, QUANTUM_LIB_SRC support

Support compiled object enclosed in library.

e.g.
```
LIB_SRC += xxxx.c
xxxx.c --> xxxx.o ---> xxxx.a
```

* remove 'ifdef/ifndef USE_I2C' from quantum/split_common/{i2c|serial}.c

* add SKIP_DEBUG_INFO into tmk_core/rules.mk

When SKIP_DEBUG_INFO=yes is specified, do not use the -g option at compile time.

* tmk_core/rules.mk: Library object need -fno-lto

* add SKIP_DEBUG_INFO=yes

* remove temporary compile test shell script

* add '#define SOFT_SERIAL_PIN D0' to keyboards/lets_split/rev?/config.h

* quantum/split_common/serial.c: Changed not to use USE_I2C.

2 files changed, 32 insertions, 8 deletions

diff --git a/tmk_core/common/command.c b/tmk_core/common/command.c
index f79d5a257b..aab99290d2 100644
--- a/tmk_core/common/command.c
+++ b/tmk_core/common/command.c
@@ -181,7 +181,11 @@ static void print_version(void)
     print("VID: " STR(VENDOR_ID) "(" STR(MANUFACTURER) ") "
           "PID: " STR(PRODUCT_ID) "(" STR(PRODUCT) ") "
           "VER: " STR(DEVICE_VER) "\n");
+#ifdef SKIP_VERSION
+    print("BUILD:  (" __DATE__ ")\n");
+#else
     print("BUILD: " STR(QMK_VERSION) " (" __TIME__ " " __DATE__ ")\n");
+#endif
 
     /* build options */
     print("OPTIONS:"
diff --git a/tmk_core/rules.mk b/tmk_core/rules.mk
index ce3cd83b3f..2e419dd667 100644
--- a/tmk_core/rules.mk
+++ b/tmk_core/rules.mk
@@ -28,12 +28,13 @@ VPATH :=
 
 # Convert all SRC to OBJ
 define OBJ_FROM_SRC
-$(patsubst %.c,$1/%.o,$(patsubst %.cpp,$1/%.o,$(patsubst %.cc,$1/%.o,$(patsubst %.S,$1/%.o,$($1_SRC)))))
+$(patsubst %.c,$1/%.o,$(patsubst %.cpp,$1/%.o,$(patsubst %.cc,$1/%.o,$(patsubst %.S,$1/%.o,$(patsubst %.clib,$1/%.a,$($1_SRC))))))
 endef
 $(foreach OUTPUT,$(OUTPUTS),$(eval $(OUTPUT)_OBJ +=$(call OBJ_FROM_SRC,$(OUTPUT))))
 
 # Define a list of all objects
 OBJ := $(foreach OUTPUT,$(OUTPUTS),$($(OUTPUT)_OBJ))
+NO_LTO_OBJ := $(filter %.a,$(OBJ))
 
 MASTER_OUTPUT := $(firstword $(OUTPUTS))
 
@@ -81,7 +82,9 @@ CSTANDARD = -std=gnu99
 #  -Wall...:     warning level
 #  -Wa,...:      tell GCC to pass this to the assembler.
 #    -adhlns...: create assembler listing
-CFLAGS += -g$(DEBUG)
+ifndef SKIP_DEBUG_INFO
+  CFLAGS += -g$(DEBUG)
+endif
 CFLAGS += $(CDEFS)
 CFLAGS += -O$(OPT)
 # add color
@@ -110,7 +113,9 @@ CFLAGS += $(CSTANDARD)
 #  -Wall...:     warning level
 #  -Wa,...:      tell GCC to pass this to the assembler.
 #    -adhlns...: create assembler listing
-CPPFLAGS += -g$(DEBUG)
+ifndef SKIP_DEBUG_INFO
+  CPPFLAGS += -g$(DEBUG)
+endif
 CPPFLAGS += $(CPPDEFS)
 CPPFLAGS += -O$(OPT)
 # to supress "warning: only initialized variables can be placed into program memory area"
@@ -138,7 +143,11 @@ CPPFLAGS += -Wa,-adhlns=$(@:%.o=%.lst)
 #  -listing-cont-lines: Sets the maximum number of continuation lines of hex
 #       dump that will be displayed for a given single line of source input.
 ASFLAGS += $(ADEFS) 
-ASFLAGS += -Wa,-adhlns=$(@:%.o=%.lst),-gstabs,--listing-cont-lines=100
+ifndef SKIP_DEBUG_INFO
+  ASFLAGS += -Wa,-adhlns=$(@:%.o=%.lst),-gstabs,--listing-cont-lines=100
+else
+  ASFLAGS += -Wa,-adhlns=$(@:%.o=%.lst),--listing-cont-lines=100
+endif
 
 #---------------- Library Options ----------------
 # Minimalistic printf version
@@ -210,6 +219,11 @@ ALL_CFLAGS = $(MCUFLAGS) $(CFLAGS) $(EXTRAFLAGS)
 ALL_CPPFLAGS = $(MCUFLAGS) -x c++ $(CPPFLAGS) $(EXTRAFLAGS)
 ALL_ASFLAGS = $(MCUFLAGS) -x assembler-with-cpp $(ASFLAGS) $(EXTRAFLAGS)
 
+define NO_LTO
+$(patsubst %.a,%.o,$1): NOLTO_CFLAGS += -fno-lto
+endef
+$(foreach LOBJ, $(NO_LTO_OBJ), $(eval $(call NO_LTO,$(LOBJ))))
+
 MOVE_DEP = mv -f $(patsubst %.o,%.td,$@) $(patsubst %.o,%.d,$@)
 
 
@@ -290,8 +304,8 @@ $1_INCFLAGS := $$(patsubst %,-I%,$$($1_INC))
 ifdef $1_CONFIG
 $1_CONFIG_FLAGS += $$(patsubst %,-include %,$$($1_CONFIG))
 endif
-$1_CFLAGS = $$(ALL_CFLAGS) $$($1_DEFS) $$($1_INCFLAGS) $$($1_CONFIG_FLAGS)
-$1_CPPFLAGS= $$(ALL_CPPFLAGS) $$($1_DEFS) $$($1_INCFLAGS) $$($1_CONFIG_FLAGS)
+$1_CFLAGS = $$(ALL_CFLAGS) $$($1_DEFS) $$($1_INCFLAGS) $$($1_CONFIG_FLAGS) $$(NOLTO_CFLAGS)
+$1_CPPFLAGS= $$(ALL_CPPFLAGS) $$($1_DEFS) $$($1_INCFLAGS) $$($1_CONFIG_FLAGS) $$(NOLTO_CFLAGS)
 $1_ASFLAGS= $$(ALL_ASFLAGS) $$($1_DEFS) $$($1_INCFLAGS) $$($1_CONFIG_FLAGS)
 
 # Compile: create object files from C source files.
@@ -321,6 +335,12 @@ $1/%.o : %.S $1/asflags.txt $1/compiler.txt | $(BEGIN)
 	$$(eval CMD=$$(CC) -c $$($1_ASFLAGS) $$< -o $$@)
 	@$$(BUILD_CMD)
 
+$1/%.a : $1/%.o
+	@mkdir -p $$(@D)
+	@$(SILENT) || printf "Archiving: $$<" | $$(AWK_CMD)
+	$$(eval CMD=$$(AR) $$@ $$<)
+	@$$(BUILD_CMD)
+
 $1/force:
 
 $1/cflags.txt: $1/force
@@ -346,7 +366,7 @@ $(MASTER_OUTPUT)/ldflags.txt: $(MASTER_OUTPUT)/force
 
 
 # We have to use static rules for the .d files for some reason
-DEPS = $(patsubst %.o,%.d,$(OBJ))
+DEPS = $(patsubst %.o,%.d,$(patsubst %.a,%.o,$(OBJ)))
 # Keep the .d files
 .PRECIOUS: $(DEPS)
 # Empty rule to force recompilation if the .d file is missing
@@ -391,7 +411,7 @@ $(shell mkdir -p $(BUILD_DIR) 2>/dev/null)
 $(eval $(foreach OUTPUT,$(OUTPUTS),$(shell mkdir -p $(OUTPUT) 2>/dev/null)))
 
 # Include the dependency files.
--include $(patsubst %.o,%.d,$(OBJ))
+-include $(patsubst %.o,%.d,$(patsubst %.a,%.o,$(OBJ)))
 
 
 # Listing of phony targets.