Adds a more sensible check for FAISS use in benchmarks. CUVS_ANN_BENCH_USE_FAISS is now set to OFF if all relevant flags are set OFF.

The status is reported in the cmake log:
-- Finding or building hnswlib
-- Checking for FAISS use in benchmarks...
-- CUVS_ANN_BENCH_USE_FAISS is OFF

Closes #1590.

Author: irina-resh-nvda

cpp/bench/ann/CMakeLists.txt

@@ -51,7 +51,31 @@ option(CUVS_KNN_BENCH_USE_CUVS_BRUTE_FORCE "Include cuVS brute force knn in benc
 
 find_package(Threads REQUIRED)
 
-set(CUVS_ANN_BENCH_USE_FAISS ON)
+# ----- FAISS use in Benchmarks ----
+get_cmake_property(_variableNames VARIABLES)
+
+set(CUVS_ANN_BENCH_USE_FAISS OFF)
+message(STATUS "Checking for FAISS use in benchmarks...")
+foreach(_varName ${_variableNames})
+    if(_varName MATCHES "CUVS_ANN_BENCH_USE_FAISS.+")
+        if(DEFINED ${_varName})
+            if(${_varName})
+                set(CUVS_ANN_BENCH_USE_FAISS ON)
+                message(STATUS "FAISS use in benchmarks detected.")
+                break()
+            endif()
+        endif()
+    endif()
+endforeach()
+
+if(CUVS_ANN_BENCH_USE_FAISS)
+    message(STATUS "CUVS_ANN_BENCH_USE_FAISS is ON")
+else()
+    message(STATUS "CUVS_ANN_BENCH_USE_FAISS is OFF")
+endif()
+
+# ----------------------------------
+
 set(CUVS_FAISS_ENABLE_GPU ON)
 set(CUVS_USE_FAISS_STATIC ON)