[llvm] [SystemZ][z/OS] define HOST_NAME_MAX for z/OS (PR #76093)

[Abhina Sree via llvm-commits]

https://github.com/abhina-sree created https://github.com/llvm/llvm-project/pull/76093

This copies the change made in google benchmark to define HOST_NAME_MAX for z/OS https://github.com/google/benchmark/commit/7b52bf7346dead5ef4f29d7f98d2a26d6194252f

>From ac66de1f1f16917c2f153da8479e1e203552c7c9 Mon Sep 17 00:00:00 2001
From: Abhina Sreeskantharajan <Abhina.Sreeskantharajan at ibm.com>
Date: Wed, 20 Dec 2023 14:04:21 -0500
Subject: [PATCH] define HOST_NAME_MAX for z/OS

---
 third-party/benchmark/src/sysinfo.cc | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/third-party/benchmark/src/sysinfo.cc b/third-party/benchmark/src/sysinfo.cc
index d9bd651f8a4d33..3a56e8cace4858 100644
--- a/third-party/benchmark/src/sysinfo.cc
+++ b/third-party/benchmark/src/sysinfo.cc
@@ -449,6 +449,8 @@ std::string GetSystemName() {
 #define HOST_NAME_MAX 154
 #elif defined(BENCHMARK_OS_RTEMS)
 #define HOST_NAME_MAX 256
+#elif defined(BENCHMARK_OS_ZOS)
+#define HOST_NAME_MAX _POSIX_HOST_NAME_MAX
 #else
 #pragma message("HOST_NAME_MAX not defined. using 64")
 #define HOST_NAME_MAX 64