It is the host directory generated in the output directory of Buildroot.

It contains absolute paths of where it has been generated, so cannot be shared directly.

To replace all absolute paths at once by the ones you are going to install the SDK to, execute:

find . -type f -name "*cmake*" -exec sed -i 's/</orig/absolute/path/to/output/host>/</new/absolute/path/to/output/host>/g' {} +

1. enable gdbserver in your Buildroot configuration (BR2_PACKAGE_GDB_SERVER), rebuild your config and flash it to your target (note: you can also just transfer the gdbserver binary to your target through ssh)
2. on your target, launch your executable with gdbserver:

   # gdbserver <your_executable> [its_arguments]

3. on your host PC, from your buildroot's config output directory, run the gdb of your toolchain:

   $ host/bin/<toolchain_prefix>-gdb   # (e.g. host/bin/aarch64-linux-gnu-gdb)

4. load the debug symbols from your staging environment:

   (gdb) set sysroot staging

5. connect gdb to gdbserver over the network:

   (gdb) target remote <target_ip>:3000  (3000 is the default port)

6. start the execution of your executable:

   (gdb) cont

From gdb you can execute step-by-step if you want, but the most interesting is probably that you can retrieve the stacktrace after a segfault, using

(gdb) bt

You can also connect to gdbserver from you IDE, if necessary.