Fix ubsan/coverage test to put coverage file in a subdirectory.
Fix ubsan/coverage test to put coverage file in a subdirectory.

By default coverage is dumped to the current directory, which may not
always be writable.

git-svn-id: c199f293c43da69278bea8e88f92242bf3aa95f7@272732 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/compiler-rt,llvm-mirror/compiler-rt,llvm-mirror/compiler-rt,llvm-mirror/compiler-rt,llvm-mirror/compiler-rt