Gave panicoverride a C implementation for now.

kernel/panicoverride.nim

@@ -1,2 +1,22 @@
-proc rawoutput(s: string) = discard
+
-proc panic(s: string) = discard
+{.push debugger:off, hints:off.}
+
+proc printf(frmt: cstring) {.varargs, importc, header: "<stdio.h>", cdecl.}
+proc exit(code: int) {.importc, header: "<stdlib.h>", cdecl.}
+
+{.push stack_trace: off, profiler:off.}
+
+proc rawoutput(s: string) =
+  printf("%s\n", s)
+
+proc panic(s: string) =
+  rawoutput(s)
+  exit(1)
+
+# Alternatively we also could implement these 2 here:
+#
+# template sysFatal(exceptn: typeDesc, message: string)
+# template sysFatal(exceptn: typeDesc, message, arg: string)
+
+{.pop.}
+{.pop.}