[clang] [llvm] [z/OS] treat text files as text files so auto-conversion is done (PR #90128)

[via llvm-commits]

zibi2 wrote:

LGTM,  but check why the following test in checks failed:
`FAIL: BOLT :: RISCV/unnamed-sym-no-entry.c`

https://github.com/llvm/llvm-project/pull/90128