Eliminate uninitialized memory problem with sigemptyset.

[SVN r77220]

src/engine/jam.c

@@ -270,7 +270,7 @@ int main( int argc, char * * argv, char * * arg_environ )
     sigprocmask(SIG_BLOCK, &sigmask, NULL);
     sa.sa_flags = 0;
     sa.sa_handler = child_sig_handler;
-    /* sigemptyset(&sa.sa_mask); */
+    sigemptyset(&sa.sa_mask);
     sigaction(SIGCHLD, &sa, NULL);
     sigemptyset(&empty_sigmask);
 #endif