Merge branch 'doc-genex-tweak' into release-3.15

Merge-request: !3939

Help/manual/cmake-generator-expressions.7.rst

@@ -195,7 +195,7 @@ Variable Queries
   .. code-block:: cmake
 
     target_compile_definitions(myapp
-      PRIVATE $<$<AND:$<COMPILE_LANGUAGE:CXX>,$<CXX_COMPILER_ID:Clang>>:COMPILING_CXX_WITH_CLANG>
+      PRIVATE $<$<AND:$<COMPILE_LANGUAGE:CXX>,$<CXX_COMPILER_ID:AppleClang,Clang>>:COMPILING_CXX_WITH_CLANG>
               $<$<AND:$<COMPILE_LANGUAGE:CXX>,$<CXX_COMPILER_ID:Intel>>:COMPILING_CXX_WITH_INTEL>
               $<$<AND:$<COMPILE_LANGUAGE:C>,$<C_COMPILER_ID:Clang>>:COMPILING_C_WITH_CLANG>
     )