I'm eventually fixing those tests the same way we manage this problem in 
libstdc++ testsuite.

    testsuite: Add optional libstdc++ version namespace in expected 
diagnostic

     When libstdc++ is build with 
--enable-symvers=gnu-versioned-namespace diagnostics are
     showing this namespace, currently __8.

     gcc/testsuite/ChangeLog:

             * 
testsuite/g++.dg/coroutines/coro-bad-alloc-00-bad-op-new.C: Add optional
             '__8' version namespace in expected diagnostic.
             * 
testsuite/g++.dg/coroutines/coro-bad-alloc-01-bad-op-del.C: Likewise.
             * 
testsuite/g++.dg/coroutines/coro-bad-alloc-02-no-op-new-nt.C: Likewise.
             * 
testsuite/g++.dg/coroutines/coro-bad-grooaf-01-grooaf-expected.C: Likewise.
             * testsuite/g++.dg/coroutines/pr97438.C: Likewise.
             * testsuite/g++.dg/coroutines/ramp-return-b.C: Likewise.

Tested under Linux x86_64.

I'm contributing to libstdc++ so I already have write access.

Ok to commit ?

François