Check only if package image exists

We don't need to look after the builder image as its optional. In this
way we can also reduce the compiler options, as we don't require a
--clean flag anymore. --only-target-package is sufficient to determine
what we can skip and how.

pkg/compiler/interface.go

@@ -49,7 +49,6 @@ type CompilerOptions struct {
 	PullFirst, KeepImg, Push bool
 	Concurrency              int
 	CompressionType          CompressionImplementation
-	Clean                    bool
 	KeepImageExport          bool
 
 	OnlyDeps        bool
@@ -68,7 +67,6 @@ func NewDefaultCompilerOptions() *CompilerOptions {
 		CompressionType: None,
 		KeepImg:         true,
 		Concurrency:     runtime.NumCPU(),
-		Clean:           true,
 		OnlyDeps:        false,
 		NoDeps:          false,
 	}