[Bug bootstrap/78251] config/gettext.m4 and config/iconv.m4 contaminate CPPFLAGS

[sch...@linux-m68k.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78251

--- Comment #6 from Andreas Schwab <sch...@linux-m68k.org> ---
If configure tests are nested then that's a bug in the way the tests are
written.