BUG: Fix ASM source file extension default list

This replaces @ASM_DIALECT@ syntax with ${ASM_DIALECT} syntax so it will
be replaced correctly.  Patch from Derek Bruening.  See issue #8639.

Modules/CMakeASMInformation.cmake

@@ -28,9 +28,9 @@ IF(NOT _INCLUDED_FILE)
   INCLUDE(Platform/${CMAKE_SYSTEM_NAME}-${CMAKE_C_COMPILER_ID}-ASM OPTIONAL)
 ENDIF(NOT _INCLUDED_FILE)
 
-IF(NOT CMAKE_ASM@ASM_DIALECT@_SOURCE_FILE_EXTENSIONS)
-  SET(CMAKE_ASM@ASM_DIALECT@_SOURCE_FILE_EXTENSIONS s;S;asm)
-ENDIF(NOT CMAKE_ASM@ASM_DIALECT@_SOURCE_FILE_EXTENSIONS)
+IF(NOT CMAKE_ASM${ASM_DIALECT}_SOURCE_FILE_EXTENSIONS)
+  SET(CMAKE_ASM${ASM_DIALECT}_SOURCE_FILE_EXTENSIONS s;S;asm)
+ENDIF(NOT CMAKE_ASM${ASM_DIALECT}_SOURCE_FILE_EXTENSIONS)
 
 IF(NOT CMAKE_ASM${ASM_DIALECT}_COMPILE_OBJECT)
   SET(CMAKE_ASM${ASM_DIALECT}_COMPILE_OBJECT "<CMAKE_ASM${ASM_DIALECT}_COMPILER> <FLAGS> -o <OBJECT> <SOURCE>")