Fix push/pop mismatch

Without this, perlhead.swg does `#pragma GCC diagnostic pop`
if `__GNUC__ >= 10` - without any prior `#pragma GCC diagnostic push`.

There's also a mismatch between the conditions that trigger
`#pragma GCC diagnostic ignored` (where the `push` should be)
and the attempt to `#pragma GCC diagnostic pop`.
2 files changed