core: move debug info and CC optimization level to config.mk

Move configuration switches CFG_DEBUG_INFO and CFG_CC_OPT_LEVEL
default values from arm.mk to config.mk and add a short description.

Signed-off-by: Etienne Carriere <etienne.carriere@linaro.org>
Reviewed-by: Jerome Forissier <jerome@forissier.org>
Reviewed-by: Jens Wiklander <jens.wiklander@linaro.org>

core/arch/arm/arm.mk

@@ -149,17 +149,8 @@ arm64-platform-cflags-no-hard-float ?= -mgeneral-regs-only
 arm64-platform-cflags-hard-float ?=
 arm64-platform-cflags-generic := -mstrict-align $(call cc-option,-mno-outline-atomics,)
 
-ifeq ($(DEBUG),1)
-# For backwards compatibility
-$(call force,CFG_CC_OPT_LEVEL,0)
-$(call force,CFG_DEBUG_INFO,y)
-endif
-
-# Optimize for size by default, usually gives good performance too
-CFG_CC_OPT_LEVEL ?= s
 platform-cflags-optimization ?= -O$(CFG_CC_OPT_LEVEL)
 
-CFG_DEBUG_INFO ?= y
 ifeq ($(CFG_DEBUG_INFO),y)
 platform-cflags-debug-info ?= -g3
 platform-aflags-debug-info ?= -g

mk/config.mk

@@ -40,6 +40,18 @@ PYTHON3 ?= python3
 
 # Define DEBUG=1 to compile without optimization (forces -O0)
 # DEBUG=1
+ifeq ($(DEBUG),1)
+# For backwards compatibility
+$(call force,CFG_CC_OPT_LEVEL,0)
+$(call force,CFG_DEBUG_INFO,y)
+endif
+
+# CFG_CC_OPT_LEVEL sets compiler optimization level passed with -O directive.
+# Optimize for size by default, usually gives good performance too.
+CFG_CC_OPT_LEVEL ?= s
+
+# Enabling CFG_DEBUG_INFO makes debug information embedded in core.
+CFG_DEBUG_INFO ?= y
 
 # If y, enable debug features of the TEE core (assertions and lock checks
 # are enabled, panic and assert messages are more verbose, data and prefetch