Genode fixes (#8501)

* Genode fixes

- wrap strings in "Genode::Cstring" when logging
- define SIGABRT for Genode
- disable GCC -fstack-protector
- use log RPC for fatal messages
- add --os:genode build to appveyor
- define paramStr and paramCount

* Select fixups for Genode POSIX

lib/system.nim

@@ -4152,8 +4152,13 @@ when defined(cpp) and appType != "lib" and
 
     let ex = getCurrentException()
     let trace = ex.getStackTrace()
-    stderr.write trace & "Error: unhandled exception: " & ex.msg &
-                 " [" & $ex.name & "]\n"
+    when defined(genode):
+      # stderr not available by default, use the LOG session
+      echo trace & "Error: unhandled exception: " & ex.msg &
+                   " [" & $ex.name & "]\n"
+    else:
+      stderr.write trace & "Error: unhandled exception: " & ex.msg &
+                   " [" & $ex.name & "]\n"
     quit 1
 
 when not defined(js):