[llvm] [SystemZ][z/OS] Query if a file is text and set the text flag accordingly (PR #109664)

[Sean Perry via llvm-commits]

perry-ca wrote:

Looks like this will also fail with header map files.  These are binary files and don't have any file tags.  The compiler will read them as EBCDIC instead as binary.

https://github.com/llvm/llvm-project/pull/109664