For debug information, get the main file name from the source manager
rather than from the -main-file-name flag, since the source manager
has proper path information. Fixes <rdar://problem/7769538>.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@98898 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed