Add an option for Waiting for gdb connection if the gdb stub configuration is chosen.

Here's a quick demonstration on how to use it(tested on M4A785T-M).
  (gdb) file ./build/cbfs/fallback/coreboot_ram.debug
  Reading symbols from [...]/build/cbfs/fallback/coreboot_ram.debug...done.
  (gdb) set remotebaud 115200
  (gdb) target remote /dev/ttyUSB0
  Remote debugging using /dev/ttyUSB0
  _text () at src/arch/x86/lib/c_start.S:85
  85		call	hardwaremain

Change-Id: Ia49cbecc41deb061433bc39f5b81715da49edc98
Signed-off-by: Denis 'GNUtoo' Carikli <GNUtoo@no-log.org>
Reviewed-on: http://review.coreboot.org/1134
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
2 files changed