Fix export cache issue

Resolve #1551 and #1020.
We are never returning the result of solved operations so Buildkit could not
cache the layer.
This commit implements a simple system to forward operations' result to the
main build to cache it.

Signed-off-by: Vasek - Tom C <tom.chauveau@epitech.eu>

pkg/universe.dagger.io/package.json

@@ -1,7 +1,7 @@
 {
   "license": "Apache-2.0",
   "scripts": {
-    "test": "bats --report-formatter junit --jobs 4 $(find . -type f -name '*.bats' -not -path '*/node_modules/*')"
+    "test": "bats --report-formatter junit --print-output-on-failure --jobs 4 $(find . -type f -name '*.bats' -not -path '*/node_modules/*')"
   },
   "devDependencies": {
     "bats": "^1.5.0",