[Bug target/58446] Support for musl libc

[gcc-bug-espfv4bhi9 at gregor dot im]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58446

--- Comment #1 from Gregor Richards <gcc-bug-espfv4bhi9 at gregor dot im> ---
Created attachment 30830
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=30830&action=edit
Fix for gomp to specify _POSIX_SOURCE requirements