If lto is enabled, we need the prefix-map variables to be passed to the linker.
Add these to the list of options libtool passes through.

Upstream-Status: Pending
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

Index: libtool-2.4.6/build-aux/ltmain.in
===================================================================
--- libtool-2.4.6.orig/build-aux/ltmain.in
+++ libtool-2.4.6/build-aux/ltmain.in
@@ -5424,9 +5424,10 @@ func_mode_link ()
       # --sysroot=*          for sysroot support
       # -O*, -g*, -flto*, -fwhopr*, -fuse-linker-plugin GCC link-time optimization
       # -stdlib=*            select c++ std lib with clang
+      # -f*-prefix-map*      needed for lto linking
       -64|-mips[0-9]|-r[0-9][0-9]*|-xarch=*|-xtarget=*|+DA*|+DD*|-q*|-m*| \
       -t[45]*|-txscale*|-p|-pg|--coverage|-fprofile-*|-F*|@*|-tp=*|--sysroot=*| \
-      -O*|-g*|-flto*|-fwhopr*|-fuse-linker-plugin|-fstack-protector*|-stdlib=*)
+      -O*|-g*|-flto*|-fwhopr*|-fuse-linker-plugin|-fstack-protector*|-stdlib=*|-f*-prefix-map*)
         func_quote_for_eval "$arg"
 	arg=$func_quote_for_eval_result
         func_append compile_command " $arg"