When compiling on a system where binutils do not yet support the 'z16'
name assembling fails with -march=native on a z16 machine.
Currently, this is interpreted as -march=z16. This patch uses -march=arch14
instead.
gcc/ChangeLog:
* config/s390/driver-native.cc (s390_host_detect_local_cpu): Use
arch14 instead of z16.