package/gcc: map debug prefix when reproducible

When building with BR2_REPRODUCIBLE the toolchain wrapper passes
-fdebug-prefix-map for all packages that are built.  But this doesn't
affect the target libraries (like libgcc) built by GCC's build system.

GCC 4.3 added a configure option to set the debug prefix map for these
libraries, which is used here to avoid encoding potentially
non-reproducible build paths into the debug data.

Signed-off-by: John Keeping <john@metanate.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>

package/gcc/gcc.mk

@@ -84,6 +84,10 @@ HOST_GCC_COMMON_CONF_OPTS = \
 	--with-bugurl="http://bugs.buildroot.net/" \
 	--without-zstd
 
+ifeq ($(BR2_REPRODUCIBLE),y)
+HOST_GCC_COMMON_CONF_OPTS += --with-debug-prefix-map=$(BASE_DIR)=buildroot
+endif
+
 # Don't build documentation. It takes up extra space / build time,
 # and sometimes needs specific makeinfo versions to work
 HOST_GCC_COMMON_CONF_ENV = \