When building with --with-tune=zEC12 and calling the resulting gcc
with --march=z13 (no extra -mtune), the binary would unexpectedly be compiled
with -march=z13 -mtune=zEC12. This patch avoids using the default tune
parameter if -march is specified as argument but the user can still
explicitly state -march=z13 -mtune=zEC12.
gcc/ChangeLog:
2018-06-26 Robin Dapp <rdapp@linux.vnet.ibm.com>
* config/s390/s390.h (enum processor_flags): Do not use
default tune parameter when -march was specified.
From-SVN: r262143
