[build] Make syscalls.h group by syscall scope

Updating the cog script to make syscalls.h more explicitly grouped by
scope.

src/libraries/j6/include/j6/syscalls.h.cog

@@ -14,12 +14,17 @@ ctx = Context(definitions_path)
 ctx.parse("syscalls.def")
 syscalls = ctx.interfaces["syscalls"]
 
+last_scope = None
 for id, scope, method in syscalls.methods:
     if scope:
         name = f"{scope.name}_{method.name}"
     else:
         name = method.name
 
+    if scope != last_scope:
+        cog.outl("")
+    last_scope = scope
+
     args = []
     if method.constructor:
         args.append("j6_handle_t *handle")