Fix braino in extract command resulting in not being able to pull bra…

…nches in a component that don't exist in perl6-bench

bench

@@ -99,7 +99,6 @@ multi MAIN ('extract', *@components) {
         my $tag-list = open 'git tag', :p;
         my @all-tags = $tag-list.lines;
         $tag-list.close;
-        %*ENV.delete('GIT_DIR');
 
         my @revs;
         if $comp<checkouts> {
@@ -118,6 +117,8 @@ multi MAIN ('extract', *@components) {
             @revs = grep / <{ $tag_regex }> /, @all-tags;
         }
 
+        %*ENV.delete('GIT_DIR');
+
         # Work around Rakudo bug #115390 by splitting into multiple loops
         for @revs -> $rev {
             if $rev.path.d {