[Profile] Mark gcov-fork test as failing for arm

Summary: instrprof-gcov-fork.test is failing with arm so mark it as XFAIL

Reviewers: marco-c

Reviewed By: marco-c

Subscribers: javed.absar, kristof.beyls, delcypher, chrib, llvm-commits, sylvestre.ledru, #sanitizers

Differential Revision: https://reviews.llvm.org/D54209

llvm-svn: 346329