CMakeDetermineASMCompiler: Fix small copy-paste mistake

GNU is not a vendor of IAR.

Modules/CMakeDetermineASMCompiler.cmake

@@ -84,7 +84,7 @@ if(NOT CMAKE_ASM${ASM_DIALECT}_COMPILER_ID)
   set(CMAKE_ASM${ASM_DIALECT}_COMPILER_ID_VENDOR_FLAGS_TI "-h")
   set(CMAKE_ASM${ASM_DIALECT}_COMPILER_ID_VENDOR_REGEX_TI "Texas Instruments")
 
-  list(APPEND CMAKE_ASM${ASM_DIALECT}_COMPILER_ID_VENDORS GNU IAR)
+  list(APPEND CMAKE_ASM${ASM_DIALECT}_COMPILER_ID_VENDORS IAR)
   set(CMAKE_ASM${ASM_DIALECT}_COMPILER_ID_VENDOR_FLAGS_IAR )
   set(CMAKE_ASM${ASM_DIALECT}_COMPILER_ID_VENDOR_REGEX_IAR "IAR Assembler")