demos/TTSArmLinux: fix missing aarch64-linux-gnu-g++ in CentOS 7

In CentOS 7, its aarch64-redhat-linux-g++.

It might be a good idea not to give a compiler name and let cmake find it by itself.

demos/TTSArmLinux/src/CMakeLists.txt

@@ -2,12 +2,12 @@ cmake_minimum_required(VERSION 3.10)
 set(CMAKE_SYSTEM_NAME Linux)
 if(ARM_ABI STREQUAL "armv8")
     set(CMAKE_SYSTEM_PROCESSOR aarch64)
-    set(CMAKE_C_COMPILER "aarch64-linux-gnu-gcc")
-    set(CMAKE_CXX_COMPILER "aarch64-linux-gnu-g++")
+    #set(CMAKE_C_COMPILER "aarch64-linux-gnu-gcc")
+    #set(CMAKE_CXX_COMPILER "aarch64-linux-gnu-g++")
 elseif(ARM_ABI STREQUAL "armv7hf")
     set(CMAKE_SYSTEM_PROCESSOR arm)
-    set(CMAKE_C_COMPILER "arm-linux-gnueabihf-gcc")
-    set(CMAKE_CXX_COMPILER "arm-linux-gnueabihf-g++")
+    #set(CMAKE_C_COMPILER "arm-linux-gnueabihf-gcc")
+    #set(CMAKE_CXX_COMPILER "arm-linux-gnueabihf-g++")
 else()
     message(FATAL_ERROR "Unknown arch abi ${ARM_ABI}, only support armv8 and armv7hf.")
     return()