rts: Ensure that forkOS releases Task on termination

Test Plan: validate

Reviewers: simonmar, erikd

Reviewed By: simonmar

Subscribers: rwbarton, thomie, carter

GHC Trac Issues: #14725

Differential Revision: https://phabricator.haskell.org/D4346

(cherry picked from commit 382c12d1)

rts/posix/OSThreads.c

@@ -223,6 +223,7 @@ forkOS_createThreadWrapper ( void * entry )
     cap = rts_lock();
     rts_evalStableIO(&cap, (HsStablePtr) entry, NULL);
     rts_unlock(cap);
+    rts_done();
     return NULL;
 }
 

rts/win32/OSThreads.c

@@ -236,6 +236,7 @@ forkOS_createThreadWrapper ( void * entry )
     cap = rts_lock();
     rts_evalStableIO(&cap, (HsStablePtr) entry, NULL);
     rts_unlock(cap);
+    rts_done();
     return 0;
 }