Merge branch 'check_cxx_compiler_flag_no_normal_variable' into release-3.19

Merge-request: !6318

Modules/Internal/CheckCompilerFlag.cmake

@@ -73,7 +73,6 @@ int main(void) { return 0; }]=])
   foreach(v IN LISTS _locale_vars)
     set(ENV{${v}} ${_locale_vars_saved_${v}})
   endforeach()
-  set(${_var} "${${_var}}" PARENT_SCOPE)
 endfunction ()
 
 cmake_policy(POP)

Tests/TryCompile/CMakeLists.txt

@@ -305,11 +305,21 @@ unset(C_BOGUS_FLAG CACHE)
 include(CheckCCompilerFlag)
 CHECK_C_COMPILER_FLAG(${C_DD}-_this_is_not_a_flag_ C_BOGUS_FLAG)
 TEST_FAIL(C_BOGUS_FLAG "CHECK_C_COMPILER_FLAG() succeeded, but should have failed")
+unset(C_BOGUS_FLAG CACHE)
+if(DEFINED C_BOGUS_FLAG)
+  # Verify that CHECK_C_COMPILER_FLAG didn't construct a normal variable
+  message(SEND_ERROR "CHECK_C_COMPILER_FLAG shouldn't construct C_BOGUS_FLAG as a normal variable")
+endif()
 
 unset(CXX_BOGUS_FLAG CACHE)
 include(CheckCXXCompilerFlag)
 CHECK_CXX_COMPILER_FLAG(${CXX_DD}-_this_is_not_a_flag_ CXX_BOGUS_FLAG)
 TEST_FAIL(CXX_BOGUS_FLAG "CHECK_CXX_COMPILER_FLAG() succeeded, but should have failed")
+unset(CXX_BOGUS_FLAG CACHE)
+if(DEFINED CXX_BOGUS_FLAG)
+  # Verify that CHECK_C_COMPILER_FLAG didn't construct a normal variable
+  message(SEND_ERROR "CHECK_CXX_COMPILER_FLAG shouldn't construct CXX_BOGUS_FLAG as a normal variable")
+endif()
 
 if(CMAKE_C_COMPILER_ID STREQUAL "GNU")
   unset(C_STRICT_PROTOTYPES CACHE)