Fix boundschecking fork for macos/SELINUX

lib/bcheck.c:
- Use INIT_SEM for child process fork on macos

tests/tests2/Makefile:
- tcc -run does not work for fork due to SHARED mmap

lib/bcheck.c

@@ -1376,6 +1376,9 @@ pid_t fork(void)
 
     WAIT_SEM();
     retval = (*fork_redir)();
+    if (retval == 0)
+        INIT_SEM();
+    else
         POST_SEM();
     return retval;
 }

tests/tests2/Makefile

@@ -94,6 +94,7 @@ GEN-ALWAYS =
     ./a.exe
 
 114_bound_signal.test: FLAGS += -b
+114_bound_signal.test: NORUN = true # tcc -run does not support fork and -b and SELINUX
 115_bound_setjmp.test: FLAGS += -b
 116_bound_setjmp2.test: FLAGS += -b
 117_builtins.test: T1 = ( $(TCC) -run $1 && $(TCC) -b -run $1 )