[Bug libgomp/69625] deadlock in libgomp.c/doacross-1.c test

[vogt at linux dot vnet.ibm.com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69625

--- Comment #1 from Dominik Vogt <vogt at linux dot vnet.ibm.com> ---
It's a bug in the S/390 backend that sometimes trashes r6 in vararg functions. 
We're working on a fix.