package/gdb: disable for nds32
There is no support for nds32 in gdb.
Fixes:
http://autobuild.buildroot.net/results/1a40b1ac5f06c856c2e30dbbb4e485022c438c72
Signed-off-by: Nylon Chen <nylon7@andestech.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>