target_arch is incorrectly set for the ppc/s390 native builds.
    The target name returned by g++ is not a subset of the target name
    passed as Make argument and therefore defaults to ia32. Adding
    a few more swap rules to set the target_arch correctly.
    This change shouldn't affect the simulator builds.

    The change to set target_arch to ia32 was added as part of:
    https://codereview.chromium.org/2045173003

R=machenbach@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com, mbrandy@us.ibm.com

BUG=
LOG=N

Review-Url: https://codereview.chromium.org/2077733002
Cr-Commit-Position: refs/heads/master@{#37071}