clang: Fix the typo for CMAKE_CXX_COMPILER_ID_TEST_FLAGS

Fix typo from commit 270e0d9c4d (Detect the correct target architecture
for clang compilers., 2020-07-28).

Issue: #21097

Modules/CMakeDetermineCXXCompiler.cmake

@@ -84,7 +84,7 @@ else()
 endif()
 
 if(CMAKE_CXX_COMPILER_TARGET)
-  list(PREPEND CMAKE_CXX_COPMILER_ID_TEST_FLAGS "-c --target=${CMAKE_CXX_COMPILER_TARGET}")
+  list(PREPEND CMAKE_CXX_COMPILER_ID_TEST_FLAGS "-c --target=${CMAKE_CXX_COMPILER_TARGET}")
 endif()
 
 # Build a small source file to identify the compiler.