https://bugs.gentoo.org/855002
https://gcc.gnu.org/PR104799
https://gcc.gnu.org/PR106102
--- a/gcc/gcc/cp/mapper-client.cc
+++ b/gcc/gcc/cp/mapper-client.cc
@@ -29,2 +29,3 @@
 #define INCLUDE_MAP
+#include <pthread.h>
 #include "system.h"
--- a/gcc/gcc/cp/mapper-resolver.cc
+++ b/gcc/gcc/cp/mapper-resolver.cc
@@ -27,2 +27,3 @@
 #define INCLUDE_MAP
+#include <pthread.h>
 #include "system.h"
--- a/gcc/gcc/cp/module.cc
+++ b/gcc/gcc/cp/module.cc
@@ -206,2 +206,3 @@
 #define INCLUDE_VECTOR
+#include <pthread.h>
 #include "system.h"
--- a/gcc/libcc1/libcc1plugin.cc
+++ b/gcc/libcc1/libcc1plugin.cc
@@ -19,2 +19,3 @@
 
+#include <pthread.h>
 #include <cc1plugin-config.h>
--- a/gcc/libcc1/libcp1plugin.cc
+++ b/gcc/libcc1/libcp1plugin.cc
@@ -20,2 +20,3 @@
 
+#include <pthread.h>
 #include <cc1plugin-config.h>