move _omitbrushes to the loading phase; this will greatly improve performance of loading a map with a ton of brushes that has most of them omitted.

qbsp/brush.cc

@@ -653,12 +653,6 @@ std::optional<bspbrush_t> LoadBrush(const mapentity_t &src, mapbrush_t &mapbrush
 
 static void Brush_LoadEntity(mapentity_t &dst, mapentity_t &src, hull_index_t hullnum, content_stats_base_t &stats, bspbrush_t::container &brushes, logging::percent_clock &clock, size_t &num_clipped)
 {
-    // _omitbrushes 1 just discards all brushes in the entity.
-    // could be useful for geometry guides, selective compilation, etc.
-    if (src.epairs.get_int("_omitbrushes")) {
-        return;
-    }
-    
     clock.max += src.mapbrushes.size();
 
     bool all_detail, all_detail_fence, all_detail_illusionary;

qbsp/map.cc

@@ -2207,6 +2207,10 @@ bool ParseEntity(parser_t &parser, mapentity_t &entity)
 
     entity.mapbrushes.clear();
 
+    // _omitbrushes 1 just discards all brushes in the entity.
+    // could be useful for geometry guides, selective compilation, etc.
+    bool omit = entity.epairs.get_int("_omitbrushes");
+
     do {
         if (!parser.parse_token())
             FError("Unexpected EOF (no closing brace)");
@@ -2216,7 +2220,16 @@ bool ParseEntity(parser_t &parser, mapentity_t &entity)
             // once we run into the first brush, set up textures state.
             EnsureTexturesLoaded();
 
+            if (omit) {
+                // skip until a } since we don't care to load brushes on this entity
+                do {
+                    if (!parser.parse_token()) {
+                        FError("Unexpected EOF (no closing brace)");
+                    }
+                } while (parser.token != "}");
+            } else {
                 entity.mapbrushes.emplace_back(ParseBrush(parser, entity));
+            }
         } else {
             ParseEpair(parser, entity);
         }