darwin.Libsystem: get pthread headers from darwin.libpthread

Some of the headers are symlinked to the root `include` in upstream
Libsystem, so also symlink them there from `include/pthread`.

pkgs/os-specific/darwin/apple-source-releases/Libsystem/default.nix

@@ -72,6 +72,10 @@ appleDerivation' stdenv {
 
     (cd ${buildPackages.darwin.cctools.dev}/include/mach-o && find . -name '*.h' | copyHierarchy $out/include/mach-o)
 
+    for header in pthread.h pthread_impl.h pthread_spis.h sched.h; do
+      ln -s "$out/include/pthread/$header" "$out/include/$header"
+    done
+
     # Copy `asl.h` from the syslog sources since it is no longer provided as part of Libc.
     cp ${syslog.src}/libsystem_asl.tproj/include/asl.h $out/include
 

pkgs/os-specific/darwin/apple-source-releases/Libsystem/headers.txt

@@ -1381,7 +1381,6 @@ protocols/routed.h
 protocols/rwhod.h
 protocols/talkd.h
 protocols/timed.h
-pthread.h
 pthread/introspection.h
 pthread/pthread.h
 pthread/pthread_impl.h
@@ -1389,9 +1388,6 @@ pthread/pthread_spis.h
 pthread/qos.h
 pthread/sched.h
 pthread/spawn.h
-pthread_impl.h
-pthread_spis.h
-pthread_workqueue.h
 pwd.h
 ranlib.h
 readpassphrase.h
@@ -1414,7 +1410,6 @@ rpc/xdr.h
 rpcsvc/yp_prot.h
 rpcsvc/ypclnt.h
 runetype.h
-sched.h
 search.h
 secure/_common.h
 secure/_stdio.h