[Bug preprocessor/108101] "#pragma once" causes other files not be included

[terra at gnome dot org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108101

--- Comment #3 from M Welinder <terra at gnome dot org> ---
Note also:

# gcc -MM c.c
c.o: c.c a.h

No b.h present!