Bug#851903: gcc-4.9 on RPi 3: gcc crashes with -mtune=native or -march=native or -mcpu=native

["Wolfgang M. Reimer" <linuxball@gmail.com>]

$ gcc -march=native -Q --help=target
*** Error in `gcc': double free or corruption (top): 0x013b8bf8 ***
Aborted
$ gcc -mcpu=native -Q --help=target
*** Error in `gcc': double free or corruption (top): 0x00536c30 ***
Aborted
$ gcc -mtune=native -Q --help=target
*** Error in `gcc': double free or corruption (top): 0x00a66c90 ***
Aborted
$