[Bug target/71749] Define _REENTRANT on ARC when -pthread is passed

[thomas.petazz...@free-electrons.com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71749

--- Comment #3 from Thomas Petazzoni <thomas.petazz...@free-electrons.com> ---
Will you submit the patch to gcc mainline yourself?