[PATCH][Revisedx2] PR55679: skip invalid tests from r194458 on darwin

[Dominique Dhumieres]

Hi jack,

> +// { dg-skip-if "Darwin lacks RLIMIT_AS in setrlimit" { *-*-darwin* } }

The comment is not fully accurate. See pr55679 comment #17 for some analysis
and another candidate patch for rlimit-mmap-test-1.c (it will detect any fix
by Apple).

Cheers,

Dominique