build: add 'qemugdb' target

This new target works much like 'make qemu' but fires up a local GDB
server on port 1234 and pauses execution

Change-Id: I87fd174c66dcc9f2f43b5b1204cc5c34f741622d
Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>

Makefile

@@ -1050,6 +1050,7 @@ help:
 	@echo  '  all		  - Build all targets marked with [*]'
 	@echo  '* zephyr	  - Build a zephyr application'
 	@echo  '  qemu		  - Build a zephyr application and run it in qemu'
+	@echo  '  qemugdb         - Same as 'qemu' but start a GDB server on port 1234'
 	@echo  '  flash		  - Build and flash an application'
 	@echo  '  debug		  - Build and debug an application using GDB'
 	@echo  ''
@@ -1168,6 +1169,9 @@ qemu: zephyr
 	$(if $(CONFIG_X86_IAMCU),python $(ZEPHYR_BASE)/scripts/qemu-machine-hack.py $(KERNEL_ELF_NAME))
 	$(Q)$(QEMU) $(QEMU_FLAGS) $(QEMU_EXTRA_FLAGS) -kernel $(KERNEL_ELF_NAME)
 
+qemugdb: QEMU_EXTRA_FLAGS += -s -S
+qemugdb: qemu
+
 -include $(srctree)/boards/$(BOARD_NAME)/Makefile.board
 ifneq ($(FLASH_SCRIPT),)
 flash: zephyr

Makefile.inc

@@ -75,9 +75,12 @@ all: $(DOTCONFIG)
 ifeq ($(findstring qemu_,$(BOARD)),)
 qemu:
 	@echo "Emulation not available for this platform"
+qemugdb: qemu
 else
 qemu: $(DOTCONFIG)
 	$(Q)$(call zephyrmake,$(O),$@)
+qemugdb: $(DOTCONFIG)
+	$(Q)$(call zephyrmake,$(O),$@)
 endif
 
 debug:	$(DOTCONFIG)