build: make prefix mapping of debug information optional

Remapping the local build path in debug information makes debugging
using ./scripts/remote-gdb harder, because files no longer refer to the full
path on the build host.

For local builds, debug information does not need to be reproducible,
since it will be stripped out of packages anyway.

For buildbot builds, it makes sense to keep debug information reproducible,
since the full path is not needed (nor desired) anywhere.

Signed-off-by: Felix Fietkau <nbd@nbd.name>

config/Config-build.in

@@ -103,6 +103,15 @@ menu "Global build settings"
 		help
 		  If enabled, buildinfo files will be stored in /etc/build.* of firmware.
 
+	config REPRODUCIBLE_DEBUG_INFO
+		bool "Make debug information reproducible"
+		default BUILDBOT
+		help
+		  This strips the local build path out of debug information. This has the
+		  advantage of making it reproducible, but the disadvantage of making local
+		  debugging using ./scripts/remote-gdb harder, since the debug data will
+		  no longer point to the full path on the build host.
+
 	config COLLECT_KERNEL_DEBUG
 		bool
 		prompt "Collect kernel debug information"

rules.mk

@@ -144,7 +144,7 @@ ifeq ($(or $(CONFIG_EXTERNAL_TOOLCHAIN),$(CONFIG_TARGET_uml)),)
   ifeq ($(CONFIG_GCC_USE_IREMAP),y)
     iremap = -iremap$(1):$(2)
   else
-    iremap = -ffile-prefix-map=$(1)=$(2)
+    iremap = -f$(if $(CONFIG_REPRODUCIBLE_DEBUG_INFO),file,macro)-prefix-map=$(1)=$(2)
   endif
 endif