Comment 8 for bug 1833798

If you have a new-enough GDB (7.9 or newer) I have a GDB Python script that will fetch symbols from the symbol server:
https://developer.mozilla.org/en-US/docs/Mozilla/Using_the_Mozilla_symbol_server#Downloading_symbols_on_Linux_Mac_OS_X

If not, there's a link there to a fetch-symbols.py script you can use to download symbols for use with GDB.