Fix cmake typo that disabled many e2e tests. (#14137)

Fixes #14133
diff --git a/build_tools/cmake/iree_check_test.cmake b/build_tools/cmake/iree_check_test.cmake
index a126c33..c30c014 100644
--- a/build_tools/cmake/iree_check_test.cmake
+++ b/build_tools/cmake/iree_check_test.cmake
@@ -276,7 +276,7 @@
   set("${_FEATURES_NAME_VAR}" "" PARENT_SCOPE)
   set("${_FEATURES_VAR}" "" PARENT_SCOPE)
   if("${_VARIANT_STRING}" STREQUAL "default")
-    set("{_ENABLED_VAR}" TRUE PARENT_SCOPE)
+    set("${_ENABLED_VAR}" TRUE PARENT_SCOPE)
     return()
   endif()
   # Interpret _VARIANT_STRING as a CMake list (;-separated).