thread_pool_run: nontermination checks at any type

So claim to return an int to appease the compiler's warning about
compartment calls.

sdk/include/thread_pool.h

diff --git a/sdk/include/thread_pool.h b/sdk/include/thread_pool.h
index c5e5d3c..cd5e4d4 100644
--- a/sdk/include/thread_pool.h
+++ b/sdk/include/thread_pool.h
@@ -45,10 +45,10 @@
   thread_pool_async(ThreadPoolCallback fn, void *data);
 
 /**
- * Run a thread pool.  This does not return and can be used as a thread entry
- * point.
+ * Run a thread pool.  This does not return, despite the claimed type, and can
+ * be used as a thread entry point.
  */
-void __cheri_compartment("thread_pool") thread_pool_run(void);
+int __cheri_compartment("thread_pool") thread_pool_run(void);
 __END_DECLS
 
 #ifdef __cplusplus

sdk/lib/thread_pool/thread_pool.cc

diff --git a/sdk/lib/thread_pool/thread_pool.cc b/sdk/lib/thread_pool/thread_pool.cc
index f58fcf9..5b8b305 100644
--- a/sdk/lib/thread_pool/thread_pool.cc
+++ b/sdk/lib/thread_pool/thread_pool.cc
@@ -47,7 +47,7 @@
 	return 0;
 }
 
-void __cheri_compartment("thread_pool") thread_pool_run()
+int __cheri_compartment("thread_pool") thread_pool_run()
 {
 	while (true)
 	{