configure: Create link to icon bitmap for out-of-tree builds

This allows to pick up the icon when starting QEMU directly from an
out-of-tree build directory.
Signed-off-by: NJan Kiszka <jan.kiszka@siemens.com>
Reviewed-by: NStefan Weil <sw@weilnetz.de>
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

configure

@@ -4369,6 +4369,7 @@ FILES="$FILES tests/tcg/lm32/Makefile po/Makefile"
 FILES="$FILES pc-bios/optionrom/Makefile pc-bios/keymaps"
 FILES="$FILES pc-bios/spapr-rtas/Makefile"
 FILES="$FILES roms/seabios/Makefile roms/vgabios/Makefile"
+FILES="$FILES pc-bios/qemu-icon.bmp"
 for bios_file in \
     $source_path/pc-bios/*.bin \
     $source_path/pc-bios/*.aml \