mkexport: Allow boards to supply custom gnu-elf.ld.

Allows boards to supply their own gnu-elf linker script, used when building Nuttx applications and CONFIG_BUILD_KERNEL.

This is useful when building fully-linked applications (see #9395).

tools/mkexport.sh

@@ -180,9 +180,13 @@ fi
 cp "${TOPDIR}/tools/mkdeps.c" "${EXPORTDIR}/tools/."
 cp "${TOPDIR}/tools/incdir.c" "${EXPORTDIR}/tools/."
 
-# Copy the default linker script
+# Copy the board specific linker if found, or use the default when not.
 
+if [ -f "${BOARDDIR}/scripts/gnu-elf.ld" ]; then
+  cp -f "${BOARDDIR}/scripts/gnu-elf.ld" "${EXPORTDIR}/scripts/."
+else
   cp -f "${TOPDIR}/binfmt/libelf/gnu-elf.ld" "${EXPORTDIR}/scripts/."
+fi
 
 # Copy the board config script