Add revdep calculation

Add CompilationSpecs type to handle slices of CompilationSpec, to
perform operation such as Unique() and Remove().

Add also dependencies and the spec associated to the Artifact, to track
how the artifact was generated.

Add revdeps compilation wrapper, and unit tests

pkg/compiler/artifact.go

@@ -25,17 +25,46 @@ import (
 	"sync"
 
 	. "github.com/mudler/luet/pkg/logger"
+	"github.com/mudler/luet/pkg/solver"
 
 	"github.com/mudler/luet/pkg/helpers"
 	"github.com/pkg/errors"
 )
 
 type PackageArtifact struct {
-	Path string
+	Path         string
+	Dependencies []Artifact
+	CompileSpec  CompilationSpec
+
+	SourceAssertion solver.PackagesAssertions
 }
 
 func NewPackageArtifact(path string) Artifact {
-	return &PackageArtifact{Path: path}
+	return &PackageArtifact{Path: path, Dependencies: []Artifact{}}
+}
+
+func (a *PackageArtifact) GetSourceAssertion() solver.PackagesAssertions {
+	return a.SourceAssertion
+}
+
+func (a *PackageArtifact) SetCompileSpec(as CompilationSpec) {
+	a.CompileSpec = as
+}
+
+func (a *PackageArtifact) GetCompileSpec() CompilationSpec {
+	return a.CompileSpec
+}
+
+func (a *PackageArtifact) SetSourceAssertion(as solver.PackagesAssertions) {
+	a.SourceAssertion = as
+}
+
+func (a *PackageArtifact) GetDependencies() []Artifact {
+	return a.Dependencies
+}
+
+func (a *PackageArtifact) SetDependencies(d []Artifact) {
+	a.Dependencies = d
 }
 
 func (a *PackageArtifact) GetPath() string {