I failed to debug the native program with NDK toolchain. Follows are my detailed steps and output.
Env Setting:
NDK_ROOT=/opt/android/ndk SYSROOT=$NDK_RO
I don't know why gdb works with the binary by ndk-build, but use file command instead of symbol-file command, it might work. gdb needs to know the image of the remote executed program.
(gdb) file hello