Run Firecracker tests one by one

Author: shym

.github/workflows/build.yml

@@ -102,7 +102,15 @@ jobs:
         run: |
           cd examples/all/
           export UNIKRAFTBACKEND=firecracker
-          opam exec -- dune runtest -j1
+          opam exec -- dune build @test-args
+          sleep 1s
+          opam exec -- dune build @test-fail
+          sleep 1s
+          opam exec -- dune build @test-hello
+          sleep 1s
+          opam exec -- dune build @test-sleeper
+          sleep 1s
+          opam exec -- dune build @test-threader
 
   mirage:
     name: Build and test a MirageOS network unikernel