esp32/Makefile: Extract common C & C++ flags for consistent compilation.

ports/esp32/Makefile

@@ -94,13 +94,20 @@ INC_ESPCOMP += -I$(ESPCOMP)/app_trace/include
 INC_ESPCOMP += -I$(ESPCOMP)/app_update/include
 INC_ESPCOMP += -I$(ESPCOMP)/pthread/include
 
-CFLAGS_BASE = -std=gnu99 -Os -ffunction-sections -fdata-sections -fstrict-volatile-bitfields -mlongcalls -nostdlib -Wall -Werror -Wno-error=unused-function -Wno-error=unused-but-set-variable -Wno-error=unused-variable -Wno-error=deprecated-declarations -DMBEDTLS_CONFIG_FILE='"mbedtls/esp_config.h"' -DHAVE_CONFIG_H -DESP_PLATFORM
+# these flags are common to C and C++ compilation
+CFLAGS_COMMON = -Os -ffunction-sections -fdata-sections -fstrict-volatile-bitfields \
+	-mlongcalls -nostdlib \
+	-Wall -Werror -Wno-error=unused-function -Wno-error=unused-but-set-variable \
+	-Wno-error=unused-variable -Wno-error=deprecated-declarations \
+	-DESP_PLATFORM
+
+CFLAGS_BASE = -std=gnu99 $(CFLAGS_COMMON) -DMBEDTLS_CONFIG_FILE='"mbedtls/esp_config.h"' -DHAVE_CONFIG_H
 CFLAGS = $(CFLAGS_BASE) $(INC) $(INC_ESPCOMP)
 CFLAGS += -DIDF_VER=\"$(IDF_VER)\"
 CFLAGS += $(CFLAGS_MOD)
 
 # this is what ESPIDF uses for c++ compilation
-CXXFLAGS = -std=gnu++11 -fno-exceptions -fno-rtti -ffunction-sections -fdata-sections -fstrict-volatile-bitfields -mlongcalls -nostdlib -Wall -Werror -Wno-error=unused-function -Wno-error=unused-but-set-variable -Wno-error=unused-variable -Wno-error=deprecated-declarations -DESP_PLATFORM $(INC) $(INC_ESPCOMP)
+CXXFLAGS = -std=gnu++11 $(CFLAGS_COMMON) $(INC) $(INC_ESPCOMP)
 
 LDFLAGS = -nostdlib -Map=$(@:.elf=.map) --cref
 LDFLAGS += --gc-sections -static -EL