[preservefiles] [users] Use the Permissions methods

- don't call out to tools (executables) when we have an API for it
  (which might call out to those tools, but that's abstracted)

src/modules/preservefiles/PreserveFiles.cpp

@@ -157,26 +157,9 @@ PreserveFiles::exec()
             {
                 if ( it.perm.isValid() )
                 {
-                    auto s_p = CalamaresUtils::System::instance();
-
-                    int r;
-
-                    r = s_p->targetEnvCall( QStringList { "chown", it.perm.username(), bare_dest } );
-                    if ( r )
-                    {
-                        cWarning() << "Could not chown target" << bare_dest;
-                    }
-
-                    r = s_p->targetEnvCall( QStringList { "chgrp", it.perm.group(), bare_dest } );
-                    if ( r )
-                    {
-                        cWarning() << "Could not chgrp target" << bare_dest;
-                    }
-
-                    r = s_p->targetEnvCall( QStringList { "chmod", it.perm.octal(), bare_dest } );
-                    if ( r )
+                    if ( !it.perm.apply( CalamaresUtils::System::instance()->targetPath( bare_dest ) ) )
                     {
-                        cWarning() << "Could not chmod target" << bare_dest;
+                        cWarning() << "Could not set attributes of" << bare_dest;
                     }
                 }
 

src/modules/users/CreateUserJob.cpp

@@ -12,6 +12,7 @@
 #include "JobQueue.h"
 #include "utils/CalamaresUtilsSystem.h"
 #include "utils/Logger.h"
+#include "utils/Permissions.h"
 
 #include <QDateTime>
 #include <QDir>
@@ -103,7 +104,7 @@ CreateUserJob::exec()
 
         if ( fileResult )
         {
-            if ( QProcess::execute( "chmod", { "440", fileResult.path() } ) )
+            if ( CalamaresUtils::Permissions::apply( fileResult.path(), 0440 ) )
             {
                 return Calamares::JobResult::error( tr( "Cannot chmod sudoers file." ) );
             }