Fix GCC conflict on new version of DEVKITARM

Author: MokhaLeee

makefile

@@ -131,6 +131,9 @@ ARCH    := -mcpu=arm7tdmi -mthumb -mthumb-interwork
 CFLAGS  := $(ARCH) $(INC_FLAG) -Wall -Wextra -Werror -Wno-unused-parameter -O2 -mtune=arm7tdmi -fno-inline -finline-functions
 ASFLAGS := $(ARCH) $(INC_FLAG)
 
+# For new version on DEVKITARM
+CFLAGS += -std=gnu99
+
 CDEPFLAGS = -MMD -MT "$*.o" -MT "$*.asm" -MF "$(CACHE_DIR)/$(notdir $*).d" -MP
 SDEPFLAGS = --MD "$(CACHE_DIR)/$(notdir $*).d"