Reorganize build options

At present, various build options are initialized at various places in
the Makefile. This patch gathers all build option declarations at the
top of the Makefile and assigns them default values.

Change-Id: I9f527bc8843bf69c00cb754dc60377bdb407a951

Makefile

@@ -28,13 +28,24 @@
 # POSSIBILITY OF SUCH DAMAGE.
 #
 
-# Decrease the verbosity of the make script
-# can be made verbose by passing V=1 at the make command line
-ifdef V
-  KBUILD_VERBOSE = ${V}
-else
-  KBUILD_VERBOSE = 0
-endif
+#
+# Default values for build configurations
+#
+
+# Build verbosity
+V			:= 0
+# Debug build
+DEBUG			:= 0
+# Build architecture
+ARCH 			:= aarch64
+# Build platform
+DEFAULT_PLAT		:= fvp
+PLAT			:= ${DEFAULT_PLAT}
+# SPD choice
+SPD			:= none
+# Base commit to perform code check on
+BASE_COMMIT		:= origin/master
+
 
 # Checkpatch ignores
 CHECK_IGNORE		=	--ignore COMPLEX_MACRO
@@ -42,17 +53,14 @@ CHECK_IGNORE		=	--ignore COMPLEX_MACRO
 CHECKPATCH_ARGS		=	--no-tree --no-signoff ${CHECK_IGNORE}
 CHECKCODE_ARGS		=	--no-patch --no-tree --no-signoff ${CHECK_IGNORE}
 
-ifeq "${KBUILD_VERBOSE}" "0"
+ifeq (${V},0)
 	Q=@
 	CHECKCODE_ARGS	+=	--no-summary --terse
 else
 	Q=
 endif
-
 export Q
 
-DEBUG	?= 0
-
 ifneq (${DEBUG}, 0)
 	BUILD_TYPE	:=	debug
 else
@@ -68,14 +76,6 @@ BL_COMMON_SOURCES	:=	common/bl_common.c			\
 				lib/io_storage.c			\
 				plat/common/aarch64/platform_helpers.S
 
-ARCH 			?=	aarch64
-
-# By default, build fvp platform
-DEFAULT_PLAT		:=	fvp
-PLAT			?=	${DEFAULT_PLAT}
-# By default, build no SPD component
-SPD			?=	none
-
 BUILD_BASE		:=	./build
 BUILD_PLAT		:=	${BUILD_BASE}/${PLAT}/${BUILD_TYPE}
 
@@ -161,28 +161,28 @@ INCLUDES		+=	-Iinclude/bl1			\
 				${PLAT_INCLUDES}		\
 				${SPD_INCLUDES}
 
+# Process DEBUG flag
+$(eval $(call assert_boolean,DEBUG))
+$(eval $(call add_define,DEBUG))
+ifeq (${DEBUG},0)
+  $(eval $(call add_define,NDEBUG))
+else
+CFLAGS			+= 	-g
+ASFLAGS			+= 	-g -Wa,--gdwarf-2
+endif
+
 ASFLAGS			+= 	-nostdinc -ffreestanding -Wa,--fatal-warnings	\
-				-mgeneral-regs-only -D__ASSEMBLY__ ${INCLUDES}	\
-				-DDEBUG=${DEBUG}
-CFLAGS			:= 	-nostdinc -pedantic -ffreestanding -Wall	\
+				-mgeneral-regs-only -D__ASSEMBLY__		\
+				${DEFINES} ${INCLUDES}
+CFLAGS			+= 	-nostdinc -pedantic -ffreestanding -Wall	\
 				-Werror -mgeneral-regs-only -std=c99 -c -Os	\
-				-DDEBUG=${DEBUG} ${INCLUDES} ${CFLAGS}
+				${DEFINES} ${INCLUDES}
 CFLAGS			+=	-ffunction-sections -fdata-sections
 
 LDFLAGS			+=	--fatal-warnings -O1
 LDFLAGS			+=	--gc-sections
 
 
-ifneq (${DEBUG}, 0)
-#CFLAGS			+= 	-g -O0
-CFLAGS			+= 	-g
-# -save-temps -fverbose-asm
-ASFLAGS			+= 	-g -Wa,--gdwarf-2
-else
-CFLAGS			+=	-DNDEBUG=1
-endif
-
-
 CC			:=	${CROSS_COMPILE}gcc
 CPP			:=	${CROSS_COMPILE}cpp
 AS			:=	${CROSS_COMPILE}gcc
@@ -193,8 +193,6 @@ OD			:=	${CROSS_COMPILE}objdump
 NM			:=	${CROSS_COMPILE}nm
 PP			:=	${CROSS_COMPILE}gcc -E ${CFLAGS}
 
-BASE_COMMIT		?=	origin/master
-
 # Variables for use with Firmware Image Package
 FIPTOOLPATH		?=	tools/fip_create
 FIPTOOL			?=	${FIPTOOLPATH}/fip_create