separate running tests with outputs from `dune build @all`

Desired Behavior

Currently when running dune build in a project where there are rules for tests that have an output file:

...
(rule                                                                                                                                                                                        
 (action                                                                                                                                                                                     
  (with-stdout-to                                                                                                                                                                            
   payloads.out                                                                                                                                                                    
   (run ./test.exe))))                                                                                                                                                            
                                                                                                                                                                                             
(rule                                                                                                                                                                                        
 (alias runtest)                                                                                                                                                                             
 (action                                                                                                                                                                                     
  (diff payloads.expected payloads.out)))
...

The first rule is built even when alias runtest is added. It would be good to be able to separate building this rule to only build during dune build @runtest because sometimes these tests are very time-consuming.

Ideally, dune build @all build test executables but do not run the executables.

For the above example, I specified the target in dune build <target.exe> which only builds the executables I want to get the desired behavior.

Example

test/test.ml:

let log = Devkit.Log.from "test" 
log#info "test is running"
Printf.print_endline "..."

test/dune

(executables      
 (libraries devkit)                                                                                                                                                                 
 (names test))

(rule                                                                                                                                                                                        
 (action                                                                                                                                                                                     
  (with-stdout-to                                                                                                                                                                            
   payloads.out                                                                                                                                                                    
   (run ./test.exe))))                                                                                                                                                            
                                                                                                                                                                                             
(rule                                                                                                                                                                                        
 (alias runtest)                                                                                                                                                                             
 (action                                                                                                                                                                                     
  (diff payloads.expected payloads.out)))

current behaviour:

$ dune build @all
[2023-01-04T01:37:01.9572] 001: [test:info] test is running

desired behaviour:

$ dune build @all

Start with the reproduction in test/test.ml and test/dune, then run dune build @all and dune build @runtest to confirm the current separation of behavior. Done means @all builds test executables without running output-producing test rules, while @runtest still runs and checks them.