Add missing license text for LGPL-2.1-or-later
Fixes: 8c1d0f13 "dbus/dbus-backtrace-win.c: New file with backtrace generator for Windows"
Sorry, I didn't spot this in !311 (merged). After merging this, !304 will need another rebase.
Fixes: 8c1d0f13 "dbus/dbus-backtrace-win.c: New file with backtrace generator for Windows"
Sorry, I didn't spot this in !311 (merged). After merging this, !304 will need another rebase.