Windows: disable status bar (#3484)

It can randomly lock inside Windows terminal emulators. Better play it
safe.

beacon_chain/conf.nim

@@ -49,8 +49,10 @@ const
 
 when defined(windows):
   {.pragma: windowsOnly.}
+  {.pragma: posixOnly, hidden.}
 else:
   {.pragma: windowsOnly, hidden.}
+  {.pragma: posixOnly.}
 
 type
   BNStartUpCmd* {.pure.} = enum
@@ -313,11 +315,13 @@ type
         name: "metrics-port" }: Port
 
       statusBarEnabled* {.
+        posixOnly
         desc: "Display a status bar at the bottom of the terminal screen"
         defaultValue: true
         name: "status-bar" }: bool
 
       statusBarContents* {.
+        posixOnly
         desc: "Textual template for the contents of the status bar"
         defaultValue: "peers: $connected_peers;" &
                       "finalized: $finalized_root:$finalized_epoch;" &

beacon_chain/nimbus_beacon_node.nim

@@ -1482,7 +1482,8 @@ func formatGwei(amount: uint64): string =
     while result[^1] == '0':
       result.setLen(result.len - 1)
 
-proc initStatusBar(node: BeaconNode) {.raises: [Defect, ValueError].} =
+when not defined(windows):
+  proc initStatusBar(node: BeaconNode) {.raises: [Defect, ValueError].} =
     if not isatty(stdout): return
     if not node.config.statusBarEnabled: return
 
@@ -1645,6 +1646,9 @@ proc doRunBeaconNode(config: var BeaconNodeConf, rng: ref BrHmacDrbgContext) {.r
   if bnStatus == BeaconNodeStatus.Stopping:
     return
 
+  when not defined(windows):
+    # This status bar can lock a Windows terminal emulator, blocking the whole
+    # event loop (seen on Windows 10, with a default MSYS2 terminal).
     initStatusBar(node)
 
   if node.nickname != "":

vendor/nim-confutils

@@ -1 +1 @@
-Subproject commit 585059d2fba17a2212fe644782a675b4a6b8dca1
+Subproject commit 9826fddd1c828112f3ad240cd3781777614ebbb4