feat: add WithInMemoryBuild to use virtual FS for kustomize

Signed-off-by: rycli <cyril@ryc.li>

cmd/flux/build_kustomization.go

@@ -72,6 +72,7 @@ type buildKsFlags struct {
 	strictSubst       bool
 	recursive         bool
 	localSources      map[string]string
+	inMemoryBuild     bool
 }
 
 var buildKsArgs buildKsFlags
@@ -85,6 +86,8 @@ func init() {
 		"When enabled, the post build substitutions will fail if a var without a default value is declared in files but is missing from the input vars.")
 	buildKsCmd.Flags().BoolVarP(&buildKsArgs.recursive, "recursive", "r", false, "Recursively build Kustomizations")
 	buildKsCmd.Flags().StringToStringVar(&buildKsArgs.localSources, "local-sources", nil, "Comma-separated list of repositories in format: Kind/namespace/name=path")
+	buildKsCmd.Flags().BoolVar(&buildKsArgs.inMemoryBuild, "in-memory-build", true,
+		"Use in-memory filesystem during build.")
 	buildCmd.AddCommand(buildKsCmd)
 }
 
@@ -130,6 +133,7 @@ func buildKsCmdRun(cmd *cobra.Command, args []string) (err error) {
 			build.WithStrictSubstitute(buildKsArgs.strictSubst),
 			build.WithRecursive(buildKsArgs.recursive),
 			build.WithLocalSources(buildKsArgs.localSources),
+			build.WithInMemoryBuild(buildKsArgs.inMemoryBuild),
 		)
 	} else {
 		builder, err = build.NewBuilder(name, buildKsArgs.path,
@@ -140,6 +144,7 @@ func buildKsCmdRun(cmd *cobra.Command, args []string) (err error) {
 			build.WithStrictSubstitute(buildKsArgs.strictSubst),
 			build.WithRecursive(buildKsArgs.recursive),
 			build.WithLocalSources(buildKsArgs.localSources),
+			build.WithInMemoryBuild(buildKsArgs.inMemoryBuild),
 		)
 	}