Preserve original code in case of standalone

Author: Maetveis

sycl/test-e2e/CMakeLists.txt

@@ -39,7 +39,7 @@ endif() # Standalone.
 
 if(SYCL_TEST_E2E_STANDALONE)
   set(SYCL_CXX_COMPILER ${CMAKE_CXX_COMPILER})
-  set(SYCL_E2E_CLANG_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
+  set(SYCL_E2E_CLANG_CXX_FLAGS ${CMAKE_CXX_FLAGS})
 else()
   set(SYCL_CXX_COMPILER "${LLVM_BINARY_DIR}/bin/clang++")
   set(SYCL_E2E_CLANG_CXX_FLAGS "" CACHE STRING