buildroot下打开gdb调试

gdb编译过程：
1.make menuconfig
2.select "gdb "in Target packages--> Debugging,profiling and benchmark --> gdb
3.select "full debugger"
4.Build options--> gcc optimization level选择optimization level 0 
5.Build options -->strip command for binaries on target选择none
6.退出menuconfig，然后make linux-reconfigure
7.cd output/target/lib; cp ../../staging/lib/libthread_db-1.0.so ./; ln -s libthread_db-1.0.so libthread_db.so.1
8.make target-post-image