boards: msp430-common: remove dead code when linking.

cpu/Makefile.include.msp430_common

@@ -3,7 +3,7 @@ export TARGET_ARCH ?= msp430
 
 # define build specific options
 CFLAGS_CPU   = -mmcu=$(CPU_MODEL)
-CFLAGS_LINK  =
+CFLAGS_LINK  = -ffunction-sections -fdata-sections
 CFLAGS_DBG   = -gdwarf-2
 CFLAGS_OPT  ?= -Os
 # export compiler flags
@@ -11,7 +11,7 @@ export CFLAGS += $(CFLAGS_CPU) $(CFLAGS_LINK) $(CFLAGS_DBG) $(CFLAGS_OPT)
 # export assmebly flags
 export ASFLAGS += $(CFLAGS_CPU) --defsym $(CPU_MODEL)=1 $(CFLAGS_DBG)
 # export linker flags
-export LINKFLAGS += $(CFLAGS_CPU) $(CFLAGS_DBG) $(CFLAGS_OPT) -static -lgcc
+export LINKFLAGS += $(CFLAGS_CPU) $(CFLAGS_DBG) $(CFLAGS_OPT) -Wl,--gc-sections -static -lgcc
 
 # Import all toolchain settings
 include $(RIOTCPU)/Makefile.include.gnu