[Support] On AIX, Check ENOTSUP on posix_fallocate instead of EOPNOTSUPP

[hubert.reinterpretcast]

Summary

posix_fallocate can fail if the underlying filesystem does not support it; and, on AIX, such a failure is reported by a return value of ENOTSUP. The existing code checks only for EOPNOTSUPP, which may share the same value as ENOTSUP, but is not required to.

[xingxue]

LGTM.

lib/Support/Unix/Path.inc

std::error_code rename(const Twine &from, const Twine &to) {
   return std::error_code();
 }
 
 std::error_code resize_file(int FD, uint64_t Size) {
 #if defined(HAVE_POSIX_FALLOCATE)
   // If we have posix_fallocate use it. Unlike ftruncate it always allocates
   // space, so we get an error if the disk is full.
   if (int Err = ::posix_fallocate(FD, 0, Size)) {
-    if (Err != EINVAL && Err != EOPNOTSUPP)
+#ifdef _AIX
+    constexpr int NotSupportedError = ENOTSUP;
+#else
+    constexpr int NotSupportedError = EOPNOTSUPP;
+#endif
+    if (Err != EINVAL && Err != NotSupportedError)
       return std::error_code(Err, std::generic_category());
   }
 #endif
   // Use ftruncate as a fallback. It may or may not allocate space. At least on
   // OS X with HFS+ it does.
   if (::ftruncate(FD, Size) == -1)
     return std::error_code(errno, std::generic_category());