[Bug preprocessor/69543] [6 Regression] _Pragma does not apply within macro

[dmalcolm at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69543

--- Comment #2 from David Malcolm <dmalcolm at gcc dot gnu.org> ---
(In reply to David Malcolm from comment #1)
linemap_compare_locations does the right thing if passed a pair of ordinary
locations, or if both locations are within the same macro expansion.

It generates nonsensical results if one of the locations is in a macro map,
which is what's happening here (the location of the _Pragma, after r232893)