[sanitizer_common] Older Haiku needs _GNU_SOURCE (#156291)

Co-authored-by: Jérôme Duval <jerome.duval@gmail.com>
GitOrigin-RevId: 27c80fba53cd44ff3d575c6049bf88ecf6c15bc2
diff --git a/lib/sanitizer_common/sanitizer_linux_libcdep.cpp b/lib/sanitizer_common/sanitizer_linux_libcdep.cpp
index f5cb85b..530ff90 100644
--- a/lib/sanitizer_common/sanitizer_linux_libcdep.cpp
+++ b/lib/sanitizer_common/sanitizer_linux_libcdep.cpp
@@ -29,6 +29,7 @@
 #  include "sanitizer_solaris.h"
 
 #  if SANITIZER_HAIKU
+#    define _GNU_SOURCE
 #    define _DEFAULT_SOURCE
 #  endif