disable werror in gdb

toolchain/gdb/gdb.mk

@@ -208,6 +208,7 @@ $(GDB_HOST_DIR)/.configured: $(GDB_DIR)/.unpacked
 		--disable-tui --disable-gdbtk --without-x \
 		--without-included-gettext \
 		--enable-threads \
+		--disable-werror \
 	)
 	touch $@