Clarify that "sandbox 1" requires linux and seccomp2

Closes 22677.

changes/bug22677

@@ -0,0 +1,3 @@
+  o Documentation:
+    - Clarify in the manual that "Sandbox 1" is only supported on Linux
+      kernels. Closes ticket 22677.

doc/tor.1.txt

@@ -558,8 +558,10 @@ GENERAL OPTIONS
 [[Sandbox]] **Sandbox** **0**|**1**::
     If set to 1, Tor will run securely through the use of a syscall sandbox.
     Otherwise the sandbox will be disabled. The option is currently an
-    experimental feature. Can not be changed while tor is running.
-
+    experimental feature. It only works on Linux-based operating systems,
+    and only when Tor has been built with the libseccomp library. This option
+    can not be changed while tor is running.
+ +
     When the Sandbox is 1, the following options can not be changed when tor
     is running:
     Address