commit 07d8d4bd2ad213281be502d6e56c19e0269b8967
author Tom de Vries <tdevries@suse.de> Fri Jul 28 16:01:51 2023 +0200
committer Tom de Vries <tdevries@suse.de> Fri Jul 28 16:01:51 2023 +0200
tree 2ff10322669f11282a09c544f9a5dde0f21b7773
parent 0c8a0b88d18d9c8d6cd52bd1a56d6ab88570f287

[gdb] Rename variable main_thread to main_thread_id

I noticed that the variable main_thread:
...
/* The main thread.  */

static std::thread::id main_thread;
...
has a confusing name and corresponding comment, because it doesn't contain the
main thread, but rather the main thread's std::thread::id.

Fix this by renaming to main_thread_id.

Tested on x86_64-linux.

Approved-By: Tom Tromey <tom@tromey.com>