Actually add indexable_ruleset to build

Done separately just in case we ever have github checks that track
files separate from cmake changes.

Signed-off-by: Mark Stemm <mark.stemm@gmail.com>

userspace/engine/CMakeLists.txt

@@ -22,6 +22,7 @@ add_library(falco_engine STATIC
     filter_details_resolver.cpp
     filter_macro_resolver.cpp
     filter_warning_resolver.cpp
+    indexable_ruleset.cpp
     logger.cpp
     stats_manager.cpp
     rule_loader.cpp