Fix __builtin_unreachable

Tomasz Konojacki pointed out on #irc that the formulation in
5d5b9c460e2a06563d2b5e35a1a79991460696eb was wrong, and the correction
here is the right way of doing it.

1 files changed, 1 insertions, 1 deletions

diff --git a/perl.h b/perl.h
index 4e252d4e23..fc39d4819b 100644
--- a/perl.h
+++ b/perl.h
@@ -3817,7 +3817,7 @@ intrinsic function, see its documents for more details.
 
 #ifdef DEBUGGING
 #  define ASSUME(x) assert(x)
-#  ifdef __builtin_unreachable
+#  if __has_builtin(__builtin_unreachable)
 #    define HAS_BUILTIN_UNREACHABLE_
 #  elif (defined(__GNUC__) && (   __GNUC__ > 4                              \
                                || __GNUC__ == 4 && __GNUC_MINOR__ >= 5))