stat a file but where mmaping it fails. In this case, we emit an
error like:
t.c:1:10: fatal error: error opening file '../../foo.h'
instead of "cannot find file".
llvm-svn: 90110
only supporting a single stat cache. The immediate benefit of this
change is that we can now generate a PCH/AST file when including
another PCH file; in the future, the chain of stat caches will likely
be useful with multiple levels of PCH files.
llvm-svn: 84263