[gold patch] Fix relro problem on ARM

[Cary Coutant <ccoutant at google dot com>]

Doug found that the PT_GNU_RELRO segment still wasn't being aligned
properly on ARM, and we discovered that if the ORDER_RELRO_LAST list
is empty (as it is for ARM), the padding we add doesn't get accounted
for when setting the segment size. This patch fixes that by adding the
padding to the increase_relro value, which is later added to the
segment size in Output_segment::set_offset(). We also added an assert
in set_offset() to verify that the RELRO segment is correctly aligned.

Tested on x86_64 and ARM. OK?

-cary (& Doug)

        * output.h (Output_segment::set_section_addresses): Pass increase_relro
        by reference; adjust all callers.
        * output.cc (Output_segment::set_section_addresses): Adjust references
        to increase_relro. Add padding to *increase_relro when ORDER_RELRO_LAST
        list is empty.
        (Output_segment::set_offset): Assert if PT_GNU_RELRO segment does not
        end at page boundary.

Attachment: gold-arm-relro-patch.txt
Description: Text document