Add some flake checks

Dependencies

• [2] CCPSI3TP Add flake.nix

Change contents

• edit in flake.nix at line 20
  [2.484]

  [2.484]
  + checks.build = hydraJobs.build.x86_64-linux;

  + checks.install = hydraJobs.tests.install.x86_64-linux;

  +