configure: add missing pc-bios/qemu_vga.ndrv symlink in build tree

Ensure that a link to pc-bios/qemu_vga.ndrv is added to the build tree,
otherwise the optional MacOS client driver will not be loaded by OpenBIOS
when launching QEMU directly from the build directory.

Signed-off-by: John Arbuckle <programmingkidx@gmail.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-Id: <20210831165020.84855-1-programmingkidx@gmail.com>
[lv: commit message rewording as suggested by Mark]
Signed-off-by: Laurent Vivier <laurent@vivier.eu>

configure

@@ -5052,7 +5052,9 @@ for bios_file in \
     $source_path/pc-bios/openbios-* \
     $source_path/pc-bios/u-boot.* \
     $source_path/pc-bios/edk2-*.fd.bz2 \
-    $source_path/pc-bios/palcode-*
+    $source_path/pc-bios/palcode-* \
+    $source_path/pc-bios/qemu_vga.ndrv
+
 do
     LINKS="$LINKS pc-bios/$(basename $bios_file)"
 done