Index: include/__threading_support
===================================================================
--- include/__threading_support
+++ include/__threading_support
@@ -19,11 +19,18 @@
 
 #ifndef _LIBCPP_HAS_NO_THREADS
 
-#if defined(_LIBCPP_HAS_THREAD_API_EXTERNAL) && (!defined(__has_include) || __has_include(<__external_threading>))
-#include <__external_threading>
+// some versions of gcc does not like it when the following two #if conditions
+// are combined into a single #if line, hence the redundancy.
+#if defined(_LIBCPP_HAS_THREAD_API_EXTERNAL)
+#  if !defined(__has_include) || __has_include(<__external_threading>)
+#    include <__external_threading>
+#  else
+#    include <pthread.h>
+#    include <sched.h>
+#  endif
 #else
-#include <pthread.h>
-#include <sched.h>
+#  include <pthread.h>
+#  include <sched.h>
 #endif
 
 #if defined(_LIBCPP_HAS_THREAD_API_EXTERNAL)