I'd like to checkout some source code once, and incrementally build it in parallel with different compilation options, using the following pipeline:

node {
  checkout scm
  stash name: 'sources'
}

parallel (
    'release': {
      node() {
        unstash 'sources'
        make BUILD=release
      }
    },

    'debug': {
      node() {
        unstash 'sources'
        make BUILD=debug
      }
    }
)  
   

It is working almost fine. The issue is that at each build, the full source code is rebuild, even if running on the same node than previous compilation.
The root cause is the untash step which is not preserving the initial file timestamp. Therefore my build system supposed every files has been modified since the last build.