AVR Support?

[mantielero]

After changing `nim.cfg`: 
    
    
    $ nim c --os:any --exceptions:quirky -d:noSignalHandler -d:danger 
-d:useMalloc hello
    Hint: used config file 
'/home/jose/.choosenim/toolchains/nim-#devel/config/nim.cfg' [Conf]
    Hint: used config file 
'/home/jose/.choosenim/toolchains/nim-#devel/config/config.nims' [Conf]
    Hint: used config file '/home/jose/src/avr/nim/nim.cfg' [Conf]
    Hint: used config file '/home/jose/src/avr/nim/borrame/nim.cfg' [Conf]
    ....
    Hint:  [Link]
    /usr/bin/avr-ld: /tmp/hello.FkAjAx.ltrans0.ltrans.o: en la función 
`checkErr_systemZio_143.part.0':
    <artificial>:(.text+0x9e6): referencia a `strerror' sin definir
    collect2: error: ld returned 1 exit status
    Error: execution of an external program failed: '/usr/bin/avr-gcc   -o 
/home/jose/src/avr/nim/borrame/hello  
/home/jose/.cache/nim/hello_r/stdlib_io.nim.c.o 
/home/jose/.cache/nim/hello_r/stdlib_system.nim.c.o 
/home/jose/.cache/nim/hello_r/@mhello.nim.c.o   -mmcu=atmega328p -flto 
-mmcu=atmega328p -flto  '
    
    
    Run

Complains about `'strerror' not defined`.