CMake:init arm64 CMake qemu-armv8a build
this patch contains arm64 Toolchain, arch common, qemu board and arm64 libc modifications.
support using CMake to compile the qemu executable file.
```
cmake -B build -DBOARD_CONFIG=qemu-armv8a:nsh -GNinja
cmake --build build -t menuconfig
cmake --build build
qemu-system-aarch64 -cpu cortex-a53 -nographic -machine virt,virtualization=on,gic-version=3 -net none -chardev stdio,id=con,mux=on -serial chardev:con -mon chardev=con,mode=readline -kernel ./nuttx
```
Signed-off-by: xuxin19 <xuxin19@xiaomi.com>
524425573e