Truly silence the attempt at loading SDL2

Expanding on https://github.com/koreader/koreader/pull/7682
ffi/input, loaded by the Device singleton, also needs to know that in
order to setup the proper input backend for SDL2.

Requires https://github.com/koreader/koreader-base/pull/1372 because
that's where the machinery for those checks live.

frontend/device.lua

@@ -1,51 +1,60 @@
 local isAndroid, _ = pcall(require, "android")
+local lfs = require("libs/libkoreader-lfs")
 local util = require("ffi/util")
 
 local function probeDevice()
     if isAndroid then
+        util.noSDL()
         return require("device/android/device")
     end
 
-    local kindle_sn = io.open("/proc/usid", "r")
-    if kindle_sn then
-        kindle_sn:close()
+    local kindle_test_stat = lfs.attributes("/proc/usid")
+    if kindle_test_stat then
+        util.noSDL()
         return require("device/kindle/device")
     end
 
-    local kg_test_stat = lfs.attributes("/bin/kobo_config.sh")
-    if kg_test_stat then
+    local kobo_test_stat = lfs.attributes("/bin/kobo_config.sh")
+    if kobo_test_stat then
+        util.noSDL()
         return require("device/kobo/device")
     end
 
     local pbook_test_stat = lfs.attributes("/ebrmain")
     if pbook_test_stat then
+        util.noSDL()
         return require("device/pocketbook/device")
     end
 
     local remarkable_test_stat = lfs.attributes("/usr/bin/xochitl")
     if remarkable_test_stat then
+        util.noSDL()
         return require("device/remarkable/device")
     end
 
     local sony_prstux_test_stat = lfs.attributes("/etc/PRSTUX")
     if sony_prstux_test_stat then
+        util.noSDL()
         return require("device/sony-prstux/device")
     end
 
     local cervantes_test_stat = lfs.attributes("/usr/bin/ntxinfo")
     if cervantes_test_stat then
+        util.noSDL()
         return require("device/cervantes/device")
     end
-    if util.isSDL() then
-        return require("device/sdl/device")
-    end
 
     -- add new ports here:
     --
     -- if --[[ implement a proper test instead --]] false then
+    --     util.noSDL()
     --     return require("device/newport/device")
     -- end
 
+    if util.isSDL() then
+        return require("device/sdl/device")
+    end
+
     error("Could not find hardware abstraction for this platform. If you are trying to run the emulator, please ensure SDL is installed.")
 end
 

setupkoenv.lua

@@ -24,7 +24,7 @@ ffi.load = function(lib)
 
     if not lib_path then
         io.write("ffi.load (warning): ", re, "\n")
-        error('Not able to load dynamic library: ' .. lib)
+        error("Not able to load dynamic library: " .. lib)
     else
         io.write("ffi.load (assisted searchpath): ", lib_path, "\n")
         return ffi_load(lib_path)