Address a few of the issues in GCDAProfiling I noted when looking through Bill's patch:
Address a few of the issues in GCDAProfiling I noted when looking
through Bill's patch:

1) Correctly test the file descriptor after the sceond attempt at
   creating the file.
2) Make the filename a global so that we can issue error messages from
   other routines.
3) Check errno in several places and print it out so that errors are
   easier to track down.

I don't really expect any of these to fix the current failures I'm
seeing, but I'm hopeful they'll at least let me debug them.

git-svn-id: c199f293c43da69278bea8e88f92242bf3aa95f7@184799 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