/tmp/cc6FtN0t.o:(.bss+0x1e8e57c): multiple definition of `_start'
/usr/lib/gcc/x86_64-linux-gnu/6/../../../x86_64-linux-gnu/Scrt1.o:(.text+0x0): first defined here
/usr/bin/ld: Warning: size of symbol `_start' changed from 43 in /usr/lib/gcc/x86_64-linux-gnu/6/../../../x86_64-linux-gnu/Scrt1.o to 4 in /tmp/cc6FtN0t.o
/usr/bin/ld: Warning: type of symbol `_start' changed from 2 to 1 in /tmp/cc6FtN0t.o
collect2: error: ld returned 1 exit status