Is need to fix the Makefile content by linux distros

Is need to fix the Makefile content by linux distros
```
$ make
cc   hello64.o   -o hello64
/usr/lib/gcc/x86_64-linux-gnu/5/../../../x86_64-linux-gnu/crt1.o: In function `_start':
(.text+0x20): undefined reference to `main'
collect2: error: ld returned 1 exit status
<builtin>: recipe for target 'hello64' failed
make: *** [hello64] Error 1
```
