[SystemZ/ZOS] Add header file to encapsulate use of <sysexits.h>

The non-standard header file `<sysexits.h>` provides some return values.
`EX_IOERR` is used to as a special value to signal a broken pipe to the clang driver.
On z/OS Unix System Services, this header file does not exists. This patch

- adds a check for `<sysexits.h>`, removing the dependency on `LLVM_ON_UNIX`
- adds a new header file `llvm/Support/ExitCodes`, which either includes
  `<sysexits.h>` or defines `EX_IOERR`
- updates the users of `EX_IOERR` to include the new header file

Reviewed By: hubert.reinterpretcast

Differential Revision: https://reviews.llvm.org/D83472

1 files changed, 1 insertions, 1 deletions

diff --git a/clang/lib/Driver/Driver.cpp b/clang/lib/Driver/Driver.cpp
index 45b5907..93b6d846 100644
--- a/clang/lib/Driver/Driver.cpp
+++ b/clang/lib/Driver/Driver.cpp
@@ -71,6 +71,7 @@
 #include "llvm/Option/Option.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/ExitCodes.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/FormatVariadic.h"
 #include "llvm/Support/Host.h"
@@ -87,7 +88,6 @@
 #include <utility>
 #if LLVM_ON_UNIX
 #include <unistd.h> // getpid
-#include <sysexits.h> // EX_IOERR
 #endif
 
 using namespace clang::driver;