I fixed few bugs when compiling elua from git on osx – clone my branch clone official repo here.

$ ./build_elua.lua board=stm32f4discovery

create .bin file

$ arm-none-eabi-objcopy -O binary elua_lua_stm32f4discovery.elf elua_lua_stm32f4discovery.bin

create openocd config file for stm32f4 board:

$ cat ~/stm32f4discovery.cfg
# stm32f4discover board
source [find interface/stlink-v2-1.cfg]
transport select hla_swd
source [find target/stm32f4x.cfg]
reset_config srst_only

and upload to the board:

$ openocd -f ~/stm32f4discovery.cfg \
   -c "init" \   
   -c "reset halt" \
   -c "sleep 100" \
   -c "wait_halt 2" 
   -c "echo \"--- Writing elua_lua_stm32f4discovery.bin\"" \
   -c "flash write_image erase elua_lua_stm32f4discovery.bin 0x08000000" \
   -c "sleep 100" \
   -c "echo \"--- Verifying\"" \
   -c "verify_image elua_lua_stm32f4discovery.bin 0x08000000" \
   -c "sleep 100" \
   -c "echo \"--- Done\"" \
   -c "resume" \
   -c "shutdown"

Open On-Chip Debugger 0.9.0 (2015-11-16-01:48)
Licensed under GNU GPL v2
For bug reports, read
	http://openocd.org/doc/doxygen/bugs.html
Info : The selected transport took over low-level target control. The results might differ compared to plain JTAG/SWD
adapter speed: 2000 kHz
adapter_nsrst_delay: 100
none separate
srst_only separate srst_nogate srst_open_drain connect_deassert_srst
Info : Unable to match requested speed 2000 kHz, using 1800 kHz
Info : Unable to match requested speed 2000 kHz, using 1800 kHz
Info : clock speed 1800 kHz
Info : STLINK v2 JTAG v25 API v2 SWIM v14 VID 0x0483 PID 0x374B
Info : using stlink api v2
Info : Target voltage: 2.884520
Info : stm32f4x.cpu: hardware has 6 breakpoints, 4 watchpoints
target state: halted
target halted due to debug-request, current mode: Thread
xPSR: 0x01000000 pc: 0x080063f0 msp: 0x20000c78
--- Writing elua_lua_stm32f4discovery.bin
auto erase enabled
Info : device id = 0x10076413
Info : flash size = 1024kbytes
wrote 262144 bytes from file elua_lua_stm32f4discovery.bin in 7.783807s (32.889 KiB/s)
--- Verifying
target state: halted
target halted due to breakpoint, current mode: Thread
xPSR: 0x61000000 pc: 0x2000002e msp: 0x20000c78
verified 220776 bytes in 2.229936s (96.685 KiB/s)
--- Done
shutdown command invoked

Now you can connect to the board using /dev/tty.usbmodem621, 115200/8/n/1. You should get this prompt:

eLua#
eLua# help
Shell commands:
  help   - shell help
  lua    - start a Lua session
  ls     - lists files and directories
  dir    - lists files and directories
  cat    - list the contents of a file
  type   - list the contents of a file
  recv   - receive files via XMODEM
  cp     - copy files
  mv     - move/rename files
  rm     - remove files
  ver    - show version information
  mkdir  - create directories
  exit   - exit the shell
For more information use 'help <command>'.
eLua# lua
Press CTRL+Z to exit Lua
Lua 5.1.4  Copyright (C) 1994-2011 Lua.org, PUC-Rio
> print(pd.board() .. "/" .. pd.platform() .. "/" .. pd.cpu())
STM32F4DISCOVERY/STM32F4/STM32F407VG

enjoy :)