[Arm] Obsoleting Command line option -mstructure-size-boundary in eabi configurations

[Michael Collison]

NetBSD/Arm requires that DEFAULT_STRUCTURE_SIZE_BOUNDARY (see 
config/arm/netbsd-elf.h for details). This patch disallows 
-mstructure-size-boundary on netbsd if the value is not equal to the 
DEFAULT_STRUCTURE_SIZE_BOUNDARY.

Okay for trunk?

2017-07-05  Michael Collison  <michael.colli...@arm.com>

        * config/arm/arm.c (arm_option_override): Disallow
        -mstructure-size-boundary on netbsd if value is not
        DEFAULT_STRUCTURE_SIZE_BOUNDARY.

pr1556.patch
Description: pr1556.patch