[Kobo] Support USBMS exports (#6552)

* \o/

* Make sure the (debug) event log doesn't end up in the fd table of our child processes...
Otherwise, it breaks USBMS.

* Close suspicious fds in the Wi-Fi scripts
To prevent any and all issues w/ USBMS down the road...

* Minor USBMS UI tweaks

* Always ask for confirmation to start on USBMS session on plug

* Bump base

https://github.com/koreader/koreader-base/pull/1161
https://github.com/koreader/koreader-base/pull/1162
https://github.com/koreader/koreader-base/pull/1163
https://github.com/koreader/koreader-base/pull/1165
https://github.com/koreader/koreader-base/pull/1167

frontend/dbg.lua

@@ -52,9 +52,15 @@ function Dbg:turnOn()
         return check
     end
 
-    --- @todo close ev.log fd for children
     -- create or clear ev log file
-    self.ev_log = io.open("ev.log", "w")
+    --- @note: On Linux, use CLOEXEC to avoid polluting the fd table of our child processes.
+    ---        Otherwise, it can be problematic w/ wpa_supplicant & USBMS...
+    ---        Note that this is entirely undocumented, but at least LuaJIT passes the mode as-is to fopen, so, we're good.
+    if jit.os == "Linux" then
+        self.ev_log = io.open("ev.log", "we")
+    else
+        self.ev_log = io.open("ev.log", "w")
+    end
 end
 
 function Dbg:turnOff()