gdb: not available on avr32

Fixes
http://autobuild.buildroot.org/results/1c6cfa7f069e2b7d8a7dacf76fbf95b7909fb37a/build-end.log.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

toolchain/gdb/Config.in

@@ -5,7 +5,7 @@ config BR2_PACKAGE_GDB
 	select BR2_PACKAGE_NCURSES
 	depends on BR2_USE_WCHAR
 	depends on BR2_TOOLCHAIN_HAS_THREADS
-	depends on !BR2_sh && !BR2_sh64
+	depends on !BR2_sh && !BR2_sh64 && !BR2_avr32
 	help
 	    Build the full gdb debugger to run on the target.