fix: avoid common CMAKE flags for variable names

Author: henryiii

tests/CMakeLists.txt

@@ -216,9 +216,9 @@ foreach(t ${PYBIND11_CROSS_MODULE_GIL_TESTS})
 endforeach()
 
 set(testdir ${CMAKE_CURRENT_SOURCE_DIR})
-foreach(target ${test_targets})
+foreach(tgt ${test_targets})
   set(test_files ${PYBIND11_TEST_FILES})
-  if(NOT TARGET STREQUAL "pybind11_tests")
+  if(NOT "${tgt}" STREQUAL "pybind11_tests")
     set(test_files "")
   endif()