boards: use a '.bin' output file when its a binary

boards/bluepill/Makefile.include

@@ -21,6 +21,7 @@ ifeq ($(PROGRAMMER),dfu-util)
   export RESET = # dfu-util has no support for resetting the device
 
   export OFLAGS = -O binary
+  HEXFILE = $(ELFFILE:.elf=.bin)
   export FFLAGS = -d 1d50:6017 -s 0x08002000:leave -D "$(HEXFILE)"
 else
 

boards/f4vi1/Makefile.include

@@ -16,5 +16,6 @@ export DEBUGSERVER = st-util
 
 # define st-flash parameters
 export OFLAGS = -O binary
+HEXFILE = $(ELFFILE:.elf=.bin)
 export FFLAGS = write $(HEXFILE) 0x8000000
 export DEBUGGER_FLAGS = $(RIOTBOARD)/$(BOARD)/dist/gdb.conf $(ELFFILE)

boards/nz32-sc151/Makefile.include

@@ -14,6 +14,7 @@ export DEBUGGER = # dfu-util has no debugger
 export RESET = # dfu-util has no support for resetting the device
 
 export OFLAGS = -O binary
+HEXFILE = $(ELFFILE:.elf=.bin)
 export FFLAGS = -d $(ID) -a 0 -s 0x08000000:leave -D "$(HEXFILE)"
 export TERMFLAGS = -p $(PORT)
 

boards/spark-core/Makefile.include

@@ -12,6 +12,7 @@ export DEBUGGER = # spark core has no debugger
 export RESET = # dfu-util has no support for resetting the device
 
 export OFLAGS = -O binary
+HEXFILE = $(ELFFILE:.elf=.bin)
 export FFLAGS = -d 1d50:607f -a 0 -s 0x08005000:leave -D "$(HEXFILE)"
 
 export INCLUDES += -I$(RIOTCPU)/$(CPU)/include/ -I$(RIOTBOARD)/$(BOARD)/include/