add option --T_dont_fork to tracee (lte-softmodem, oaisim)

The T has 2 processes: the tracee and the local tracer
if the tracee dies (segfault or whatever) the tracee
may still be running.

So there is a third process that monitors those two others
and kill everything when one dies.

The problem is that this third process has to be the parent
of the two others. That makes debugging the tracee with gdb
impossible. This new option disables the third monitor process.

common/utils/T/T.c

@@ -107,7 +107,7 @@ static void monitor_and_kill(int child1, int child2)
   exit(0);
 }
 
-void T_init(int remote_port, int wait_for_tracer)
+void T_init(int remote_port, int wait_for_tracer, int dont_fork)
 {
   int socket_pair[2];
   int s;
@@ -117,7 +117,7 @@ void T_init(int remote_port, int wait_for_tracer)
   if (socketpair(AF_UNIX, SOCK_STREAM, 0, socket_pair))
     { perror("socketpair"); abort(); }
 
-  /* child1 runs the local tracer and child2 runs the tracee */
+  /* child1 runs the local tracer and child2 (or main) runs the tracee */
 
   child1 = fork(); if (child1 == -1) abort();
   if (child1 == 0) {
@@ -127,10 +127,12 @@ void T_init(int remote_port, int wait_for_tracer)
   }
   close(socket_pair[0]);
 
-  child2 = fork(); if (child2 == -1) abort();
-  if (child2 != 0) {
-    close(socket_pair[1]);
-    monitor_and_kill(child1, child2);
+  if (dont_fork == 0) {
+    child2 = fork(); if (child2 == -1) abort();
+    if (child2 != 0) {
+      close(socket_pair[1]);
+      monitor_and_kill(child1, child2);
+    }
   }
 
   s = socket_pair[1];

common/utils/T/T.h

@@ -562,7 +562,7 @@ extern T_cache_t *T_cache;
 
 extern int *T_active;
 
-void T_init(int remote_port, int wait_for_tracer);
+void T_init(int remote_port, int wait_for_tracer, int dont_fork);
 
 #else /* T_TRACER */