Update test/conformance/CMakeLists.txt

Co-authored-by: Omar Ahmed <omarpiratee2010@gmail.com>

Author: martygrant

test/conformance/CMakeLists.txt

@@ -160,7 +160,7 @@ if(UR_DPCXX)
         add_subdirectory(${dir})
     endforeach()
 else()
-    set(DISABLED_TESTS)
+    set(DISABLED_TESTS "")
     foreach(dir ${TEST_SUBDIRECTORIES_DPCXX})
         if(NOT dir STREQUAL "device_code")
             list(APPEND DISABLED_TESTS "test-${dir}")