toolchain,build: prefer -ffile-prefix-map for gcc-8+

-ffile-prefix-map=OLD=NEW is an alias for both -fdebug-prefix-map and
-fmacro-prefix-map and is available since GCC 8.

Co-Developed-by: Andre Heider <a.heider@gmail.com>
Signed-off-by: Andre Heider <a.heider@gmail.com>
Signed-off-by: Paul Spooren <mail@aparcar.org>
[refactored into separate commit]
Signed-off-by: Petr Štetiar <ynezz@true.cz>

rules.mk

@@ -140,11 +140,11 @@ else
   TOOLCHAIN_DIR_NAME:=toolchain-$(GNU_TARGET_NAME)
 endif
 
-ifeq ($(or $(CONFIG_EXTERNAL_TOOLCHAIN),$(CONFIG_GCC_VERSION_4_8),$(CONFIG_TARGET_uml)),)
-  ifeq ($(CONFIG_GCC_USE_EMBEDDED_PATH_REMAP),y)
-    iremap = -fmacro-prefix-map=$(1)=$(2)
-  else
+ifeq ($(or $(CONFIG_EXTERNAL_TOOLCHAIN),$(CONFIG_TARGET_uml)),)
+  ifeq ($(CONFIG_GCC_USE_IREMAP),y)
     iremap = -iremap$(1):$(2)
+  else
+    iremap = -ffile-prefix-map=$(1)=$(2)
   endif
 endif
 

toolchain/gcc/Config.in

@@ -22,6 +22,11 @@ choice
 		bool "gcc 9.x"
 endchoice
 
+config GCC_USE_IREMAP
+	default y if ( GCC_USE_VERSION_5 || GCC_USE_VERSION_7 )
+	default n
+	bool
+
 config GCC_USE_GRAPHITE
 	bool
 	prompt "Compile in support for the new Graphite framework in GCC 4.4+" if TOOLCHAINOPTS

toolchain/gcc/Config.version

@@ -11,11 +11,6 @@ config GCC_VERSION_9
 	default y if GCC_USE_VERSION_9
 	bool
 
-config GCC_USE_EMBEDDED_PATH_REMAP
-	default y if ( GCC_VERSION_8 || GCC_VERSION_9 )
-	default n
-	bool
-
 config GCC_VERSION
 	string
 	default "5.5.0"		if GCC_VERSION_5